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2.1 Built-in Functions

The Python interpreter has a number of functions built into it that are always available. They are listed here in alphabetical order.

`__import__`(name[, globals[, locals[, fromlist]]])
  This function is invoked by the `import` statement. It mainly exists so that you can replace it with another function that has a compatible interface, in order to change the semantics of the `import` statement. For examples of why and how you would do this, see the standard library modules `ihooks` and `rexec` . See also the built-in module `imp` , which defines some useful operations out of which you can build your own `__import__()` function.

  For example, the statement "`import spam`" results in the following call: `__import__('spam',` `globals(),` `locals(), [])`; the statement "`from spam.ham import eggs`" results in "`__import__('spam.ham', globals(), locals(), ['eggs'])`". Note that even though `locals()` and `['eggs']` are passed in as arguments, the `__import__()` function does not set the local variable named `eggs`; this is done by subsequent code that is generated for the import statement. (In fact, the standard implementation does not use its locals argument at all, and uses its globals only to determine the package context of the `import` statement.)

  When the name variable is of the form `package.module`, normally, the top-level package (the name up till the first dot) is returned, not the module named by name. However, when a non-empty fromlist argument is given, the module named by name is returned. This is done for compatibility with the bytecode generated for the different kinds of import statement; when using "`import spam.ham.eggs`", the top-level package `spam` must be placed in the importing namespace, but when using "`from spam.ham import eggs`", the `spam.ham` subpackage must be used to find the `eggs` variable. As a workaround for this behavior, use `getattr()` to extract the desired components. For example, you could define the following helper:

        import string

        def my_import(name):
            mod = __import__(name)
            components = string.split(name, '.')
            for comp in components[1:]:
                mod = getattr(mod, comp)
            return mod

`abs`(x)
  Return the absolute value of a number. The argument may be a plain or long integer or a floating point number. If the argument is a complex number, its magnitude is returned.

`apply`(function, args[, keywords])
  The function argument must be a callable object (a user-defined or built-in function or method, or a class object) and the args argument must be a sequence. The function is called with args as the argument list; the number of arguments is the the length of the tuple. If the optional keywords argument is present, it must be a dictionary whose keys are strings. It specifies keyword arguments to be added to the end of the the argument list. Calling `apply()` is different from just calling `function(args)`, since in that case there is always exactly one argument. The use of `apply()` is equivalent to `function(*args, **keywords)`.

`buffer`(object[, offset[, size]])
  The object argument must be an object that supports the buffer call interface (such as strings, arrays, and buffers). A new buffer object will be created which references the object argument. The buffer object will be a slice from the beginning of object (or from the specified offset). The slice will extend to the end of object (or will have a length given by the size argument).

`callable`(object)
  Return true if the object argument appears callable, false if not. If this returns true, it is still possible that a call fails, but if it is false, calling object will never succeed. Note that classes are callable (calling a class returns a new instance); class instances are callable if they have a `__call__()` method.

`chr`(i)
  Return a string of one character whose ASCII code is the integer i. For example, `chr(97)` returns the string `'a'`. This is the inverse of `ord()`. The argument must be in the range [0..255], inclusive; `ValueError` will be raised if i is outside that range.

`cmp`(x, y)
  Compare the two objects x and y and return an integer according to the outcome. The return value is negative if `x < y`, zero if `x == y` and strictly positive if `x > y`.

`coerce`(x, y)
  Return a tuple consisting of the two numeric arguments converted to a common type, using the same rules as used by arithmetic operations.

`compile`(string, filename, kind[, flags[, dont_inherit]])
  Compile the string into a code object. Code objects can be executed by an `exec` statement or evaluated by a call to `eval()`. The filename argument should give the file from which the code was read; pass some recognizable value if it wasn't read from a file (`'<string>'` is commonly used). The kind argument specifies what kind of code must be compiled; it can be `'exec'` if string consists of a sequence of statements, `'eval'` if it consists of a single expression, or `'single'` if it consists of a single interactive statement (in the latter case, expression statements that evaluate to something else than `None` will printed).

  When compiling multi-line statements, two caveats apply: line endings must be represented by a single newline character (`'\n'`), and the input must be terminated by at least one newline character. If line endings are represented by `'\r\n'`, use the string `replace()` method to change them into `'\n'`.

  The optional arguments flags and dont_inherit (which are new in Python 2.2) control which future statements (see PEP 236) affect the compilation of string. If neither is present (or both are zero) the code is compiled with those future statements that are in effect in the code that is calling compile. If the flags argument is given and dont_inherit is not (or is zero) then the future statements specified by the flags argument are used in addition to those that would be used anyway. If dont_inherit is a non-zero integer then the flags argument is it - the future statements in effect around the call to compile are ignored.

  Future statemants are specified by bits which can be bitwise or-ed together to specify multiple statements. The bitfield required to specify a given feature can be found as the `compiler_flag` attribute on the `_Feature` instance in the `__future__` module.

`complex`(real[, imag])
  Create a complex number with the value real + imag*j or convert a string or number to a complex number. If the first parameter is a string, it will be interpreted as a complex number and the function must be called without a second parameter. The second parameter can never be a string. Each argument may be any numeric type (including complex). If imag is omitted, it defaults to zero and the function serves as a numeric conversion function like `int()`, `long()` and `float()`.

`delattr`(object, name)
  This is a relative of `setattr()`. The arguments are an object and a string. The string must be the name of one of the object's attributes. The function deletes the named attribute, provided the object allows it. For example, `delattr(x, 'foobar')` is equivalent to `del x.foobar`.

`dict`([mapping-or-sequence])
  Return a new dictionary initialized from the optional argument. If an argument is not specified, return a new empty dictionary. If the argument is a mapping object, return a dictionary mapping the same keys to the same values as does the mapping object. Else the argument must be a sequence, a container that supports iteration, or an iterator object. The elements of the argument must each also be of one of those kinds, and each must in turn contain exactly two objects. The first is used as a key in the new dictionary, and the second as the key's value. If a given key is seen more than once, the last value associated with it is retained in the new dictionary. For example, these all return a dictionary equal to `{1: 2, 2: 3}`:

  - `dict({1: 2, 2: 3})`
  - `dict({1: 2, 2: 3}.items())`
  - `dict({1: 2, 2: 3}.iteritems())`
  - `dict(zip((1, 2), (2, 3)))`
  - `dict([[2, 3], [1, 2]])`
  - `dict([(i-1, i) for i in (2, 3)])`

  New in version 2.2.

`dir`([object])
  Without arguments, return the list of names in the current local symbol table. With an argument, attempts to return a list of valid attributes for that object. This information is gleaned from the object's `__dict__` attribute, if defined, and from the class or type object. The list is not necessarily complete. If the object is a module object, the list contains the names of the module's attributes. If the object is a type or class object, the list contains the names of its attributes, and recursively of the attributes of its bases. Otherwise, the list contains the object's attributes' names, the names of its class's attributes, and recursively of the attributes of its class's base classes. The resulting list is sorted alphabetically. For example:

        >>> import struct
        >>> dir()
        ['__builtins__', '__doc__', '__name__', 'struct']
        >>> dir(struct)
        ['__doc__', '__name__', 'calcsize', 'error', 'pack', 'unpack']

  Note: Because `dir()` is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries to supply a rigorously or consistently defined set of names, and its detailed behavior may change across releases.

`divmod`(a, b)
  Take two numbers as arguments and return a pair of numbers consisting of their quotient and remainder when using long division. With mixed operand types, the rules for binary arithmetic operators apply. For plain and long integers, the result is the same as `(a / b, a % b)`. For floating point numbers the result is `(q, a % b)`, where q is usually `math.floor(a / b)` but may be 1 less than that. In any case `q * b + a % b` is very close to a, if `a % b` is non-zero it has the same sign as b, and `0 <= abs(a % b) < abs(b)`.

`eval`(expression[, globals[, locals]])
  The arguments are a string and two optional dictionaries. The expression argument is parsed and evaluated as a Python expression (technically speaking, a condition list) using the globals and locals dictionaries as global and local name space. If the locals dictionary is omitted it defaults to the globals dictionary. If both dictionaries are omitted, the expression is executed in the environment where `eval` is called. The return value is the result of the evaluated expression. Syntax errors are reported as exceptions. Example:

        >>> x = 1
        >>> print eval('x+1')
        2

  This function can also be used to execute arbitrary code objects (such as those created by `compile()`). In this case pass a code object instead of a string. The code object must have been compiled passing `'eval'` as the kind argument.

  Hints: dynamic execution of statements is supported by the `exec` statement. Execution of statements from a file is supported by the `execfile()` function. The `globals()` and `locals()` functions returns the current global and local dictionary, respectively, which may be useful to pass around for use by `eval()` or `execfile()`.

`execfile`(file[, globals[, locals]])
  This function is similar to the `exec` statement, but parses a file instead of a string. It is different from the `import` statement in that it does not use the module administration -- it reads the file unconditionally and does not create a new module.2.2

  The arguments are a file name and two optional dictionaries. The file is parsed and evaluated as a sequence of Python statements (similarly to a module) using the globals and locals dictionaries as global and local namespace. If the locals dictionary is omitted it defaults to the globals dictionary. If both dictionaries are omitted, the expression is executed in the environment where `execfile()` is called. The return value is `None`.

  Warning: The default locals act as described for function `locals()` below: modifications to the default locals dictionary should not be attempted. Pass an explicit locals dictionary if you need to see effects of the code on locals after function `execfile()` returns. `execfile()` cannot be used reliably to modify a function's locals.

`file`(filename[, mode[, bufsize]])
  Return a new file object (described earlier under Built-in Types). The first two arguments are the same as for `stdio`'s `fopen()`: filename is the file name to be opened, mode indicates how the file is to be opened: `'r'` for reading, `'w'` for writing (truncating an existing file), and `'a'` opens it for appending (which on some Unix systems means that all writes append to the end of the file, regardless of the current seek position).

  Modes `'r+'`, `'w+'` and `'a+'` open the file for updating (note that `'w+'` truncates the file). Append `'b'` to the mode to open the file in binary mode, on systems that differentiate between binary and text files (else it is ignored). If the file cannot be opened, `IOError` is raised.

  If mode is omitted, it defaults to `'r'`. When opening a binary file, you should append `'b'` to the mode value for improved portability. (It's useful even on systems which don't treat binary and text files differently, where it serves as documentation.) The optional bufsize argument specifies the file's desired buffer size: 0 means unbuffered, 1 means line buffered, any other positive value means use a buffer of (approximately) that size. A negative bufsize means to use the system default, which is usually line buffered for for tty devices and fully buffered for other files. If omitted, the system default is used.2.3

  The `file()` constructor is new in Python 2.2. The previous spelling, `open()`, is retained for compatibility, and is an alias for `file()`.

`filter`(function, list)
  Construct a list from those elements of list for which function returns true. list may be either a sequence, a container which supports iteration, or an iterator, If list is a string or a tuple, the result also has that type; otherwise it is always a list. If function is `None`, the identity function is assumed, that is, all elements of list that are false (zero or empty) are removed.

`float`(x)
  Convert a string or a number to floating point. If the argument is a string, it must contain a possibly signed decimal or floating point number, possibly embedded in whitespace; this behaves identical to `string.atof(x)`. Otherwise, the argument may be a plain or long integer or a floating point number, and a floating point number with the same value (within Python's floating point precision) is returned.

  Note: When passing in a string, values for NaN and Infinity may be returned, depending on the underlying C library. The specific set of strings accepted which cause these values to be returned depends entirely on the C library and is known to vary.

`getattr`(object, name[, default])
  Return the value of the named attributed of object. name must be a string. If the string is the name of one of the object's attributes, the result is the value of that attribute. For example, `getattr(x, 'foobar')` is equivalent to `x.foobar`. If the named attribute does not exist, default is returned if provided, otherwise `AttributeError` is raised.

`globals`()
  Return a dictionary representing the current global symbol table. This is always the dictionary of the current module (inside a function or method, this is the module where it is defined, not the module from which it is called).

`hasattr`(object, name)
  The arguments are an object and a string. The result is 1 if the string is the name of one of the object's attributes, 0 if not. (This is implemented by calling `getattr(object, name)` and seeing whether it raises an exception or not.)

`hash`(object)
  Return the hash value of the object (if it has one). Hash values are integers. They are used to quickly compare dictionary keys during a dictionary lookup. Numeric values that compare equal have the same hash value (even if they are of different types, as is the case for 1 and 1.0).

`help`([object])
  Invoke the built-in help system. (This function is intended for interactive use.) If no argument is given, the interactive help system starts on the interpreter console. If the argument is a string, then the string is looked up as the name of a module, function, class, method, keyword, or documentation topic, and a help page is printed on the console. If the argument is any other kind of object, a help page on the object is generated.

`hex`(x)
  Convert an integer number (of any size) to a hexadecimal string. The result is a valid Python expression. Note: this always yields an unsigned literal. For example, on a 32-bit machine, `hex(-1)` yields `'0xffffffff'`. When evaluated on a machine with the same word size, this literal is evaluated as -1; at a different word size, it may turn up as a large positive number or raise an `OverflowError` exception.

`id`(object)
  Return the `identity' of an object. This is an integer (or long integer) which is guaranteed to be unique and constant for this object during its lifetime. Two objects whose lifetimes are disjunct may have the same `id()` value. (Implementation note: this is the address of the object.)

`input`([prompt])
  Equivalent to `eval(raw_input(prompt))`. Warning: This function is not safe from user errors! It expects a valid Python expression as input; if the input is not syntactically valid, a `SyntaxError` will be raised. Other exceptions may be raised if there is an error during evaluation. (On the other hand, sometimes this is exactly what you need when writing a quick script for expert use.)

  If the `readline` module was loaded, then `input()` will use it to provide elaborate line editing and history features.

  Consider using the `raw_input()` function for general input from users.

`int`(x[, radix])
  Convert a string or number to a plain integer. If the argument is a string, it must contain a possibly signed decimal number representable as a Python integer, possibly embedded in whitespace; this behaves identical to `string.atoi(x[, radix])`. The radix parameter gives the base for the conversion and may be any integer in the range [2, 36], or zero. If radix is zero, the proper radix is guessed based on the contents of string; the interpretation is the same as for integer literals. If radix is specified and x is not a string, `TypeError` is raised. Otherwise, the argument may be a plain or long integer or a floating point number. Conversion of floating point numbers to integers truncates (towards zero).

`intern`(string)
  Enter string in the table of ``interned'' strings and return the interned string - which is string itself or a copy. Interning strings is useful to gain a little performance on dictionary lookup - if the keys in a dictionary are interned, and the lookup key is interned, the key comparisons (after hashing) can be done by a pointer compare instead of a string compare. Normally, the names used in Python programs are automatically interned, and the dictionaries used to hold module, class or instance attributes have interned keys. Interned strings are immortal (never get garbage collected).

`isinstance`(object, classinfo)
  Return true if the object argument is an instance of the classinfo argument, or of a (direct or indirect) subclass thereof. Also return true if classinfo is a type object and object is an object of that type. If object is not a class instance or a object of the given type, the function always returns false. If classinfo is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence types are not accepted). If classinfo is not a class, type, or tuple of classes, types, and such tuples, a `TypeError` exception is raised. Changed in version 2.2: Support for a tuple of type information was added.

`issubclass`(class1, class2)
  Return true if class1 is a subclass (direct or indirect) of class2. A class is considered a subclass of itself. If either argument is not a class object, a `TypeError` exception is raised.

`iter`(o[, sentinel])
  Return an iterator object. The first argument is interpreted very differently depending on the presence of the second argument. Without a second argument, o must be a collection object which supports the iteration protocol (the `__iter__()` method), or it must support the sequence protocol (the `__getitem__()` method with integer arguments starting at `0`). If it does not support either of those protocols, `TypeError` is raised. If the second argument, sentinel, is given, then o must be a callable object. The iterator created in this case will call o with no arguments for each call to its `next()` method; if the value returned is equal to sentinel, `StopIteration` will be raised, otherwise the value will be returned. New in version 2.2.

`len`(s)
  Return the length (the number of items) of an object. The argument may be a sequence (string, tuple or list) or a mapping (dictionary).

`list`([sequence])
  Return a list whose items are the same and in the same order as sequence's items. sequence may be either a sequence, a container that supports iteration, or an iterator object. If sequence is already a list, a copy is made and returned, similar to `sequence[:]`. For instance, `list('abc')` returns `['a', 'b', 'c']` and `list( (1, 2, 3) )` returns `[1, 2, 3]`.

`locals`()
  Return a dictionary representing the current local symbol table. Warning: The contents of this dictionary should not be modified; changes may not affect the values of local variables used by the interpreter.

`long`(x[, radix])
  Convert a string or number to a long integer. If the argument is a string, it must contain a possibly signed number of arbitrary size, possibly embedded in whitespace; this behaves identical to `string.atol(x)`. The radix argument is interpreted in the same way as for `int()`, and may only be given when x is a string. Otherwise, the argument may be a plain or long integer or a floating point number, and a long integer with the same value is returned. Conversion of floating point numbers to integers truncates (towards zero).

`map`(function, list, ...)
  Apply function to every item of list and return a list of the results. If additional list arguments are passed, function must take that many arguments and is applied to the items of all lists in parallel; if a list is shorter than another it is assumed to be extended with `None` items. If function is `None`, the identity function is assumed; if there are multiple list arguments, `map()` returns a list consisting of tuples containing the corresponding items from all lists (a kind of transpose operation). The list arguments may be any kind of sequence; the result is always a list.

`max`(s[, args...])
  With a single argument s, return the largest item of a non-empty sequence (such as a string, tuple or list). With more than one argument, return the largest of the arguments.

`min`(s[, args...])
  With a single argument s, return the smallest item of a non-empty sequence (such as a string, tuple or list). With more than one argument, return the smallest of the arguments.

`oct`(x)
  Convert an integer number (of any size) to an octal string. The result is a valid Python expression. Note: this always yields an unsigned literal. For example, on a 32-bit machine, `oct(-1)` yields `'037777777777'`. When evaluated on a machine with the same word size, this literal is evaluated as -1; at a different word size, it may turn up as a large positive number or raise an `OverflowError` exception.

`open`(filename[, mode[, bufsize]])
  An alias for the `file()` function above.

`ord`(c)
  Return the ASCII value of a string of one character or a Unicode character. E.g., `ord('a')` returns the integer `97`, `ord(u'
  u2020')` returns `8224`. This is the inverse of `chr()` for strings and of `unichr()` for Unicode characters.

`pow`(x, y[, z])
  Return x to the power y; if z is present, return x to the power y, modulo z (computed more efficiently than `pow(x, y) % z`). The arguments must have numeric types. With mixed operand types, the coercion rules for binary arithmetic operators apply. For int and long int operands, the result has the same type as the operands (after coercion) unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, `10**2` returns `100`, but `10**-2` returns `0.01`. (This last feature was added in Python 2.2. In Python 2.1 and before, if both arguments were of integer types and the second argument was negative, an exception was raised.) If the second argument is negative, the third argument must be omitted. If z is present, x and y must be of integer types, and y must be non-negative. (This restriction was added in Python 2.2. In Python 2.1 and before, floating 3-argument `pow()` returned platform-dependent results depending on floating-point rounding accidents.)

`range`([start,] stop[, step])
  This is a versatile function to create lists containing arithmetic progressions. It is most often used in `for` loops. The arguments must be plain integers. If the step argument is omitted, it defaults to `1`. If the start argument is omitted, it defaults to `0`. The full form returns a list of plain integers `[start, start + step, start + 2 * step, ...]`. If step is positive, the last element is the largest `start + i * step` less than stop; if step is negative, the last element is the largest `start + i * step` greater than stop. step must not be zero (or else `ValueError` is raised). Example:

        >>> range(10)
        [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
        >>> range(1, 11)
        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
        >>> range(0, 30, 5)
        [0, 5, 10, 15, 20, 25]
        >>> range(0, 10, 3)
        [0, 3, 6, 9]
        >>> range(0, -10, -1)
        [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
        >>> range(0)
        []
        >>> range(1, 0)
        []

`raw_input`([prompt])
  If the prompt argument is present, it is written to standard output without a trailing newline. The function then reads a line from input, converts it to a string (stripping a trailing newline), and returns that. When EOF is read, `EOFError` is raised. Example:

        >>> s = raw_input('--> ')
        --> Monty Python's Flying Circus
        >>> s
        "Monty Python's Flying Circus"

  If the `readline` module was loaded, then `raw_input()` will use it to provide elaborate line editing and history features.

`reduce`(function, sequence[, initializer])
  Apply function of two arguments cumulatively to the items of sequence, from left to right, so as to reduce the sequence to a single value. For example, `reduce(lambda x, y: x+y, [1, 2, 3, 4, 5])` calculates `((((1+2)+3)+4)+5)`. If the optional initializer is present, it is placed before the items of the sequence in the calculation, and serves as a default when the sequence is empty.

`reload`(module)
  Re-parse and re-initialize an already imported module. The argument must be a module object, so it must have been successfully imported before. This is useful if you have edited the module source file using an external editor and want to try out the new version without leaving the Python interpreter. The return value is the module object (the same as the module argument).

  There are a number of caveats:

  If a module is syntactically correct but its initialization fails, the first `import` statement for it does not bind its name locally, but does store a (partially initialized) module object in `sys.modules`. To reload the module you must first `import` it again (this will bind the name to the partially initialized module object) before you can `reload()` it.

  When a module is reloaded, its dictionary (containing the module's global variables) is retained. Redefinitions of names will override the old definitions, so this is generally not a problem. If the new version of a module does not define a name that was defined by the old version, the old definition remains. This feature can be used to the module's advantage if it maintains a global table or cache of objects -- with a `try` statement it can test for the table's presence and skip its initialization if desired.

  It is legal though generally not very useful to reload built-in or dynamically loaded modules, except for `sys`, `__main__` and `__builtin__`. In many cases, however, extension modules are not designed to be initialized more than once, and may fail in arbitrary ways when reloaded.

  If a module imports objects from another module using `from` ... `import` ..., calling `reload()` for the other module does not redefine the objects imported from it -- one way around this is to re-execute the `from` statement, another is to use `import` and qualified names (module.name) instead.

  If a module instantiates instances of a class, reloading the module that defines the class does not affect the method definitions of the instances -- they continue to use the old class definition. The same is true for derived classes.

`repr`(object)
  Return a string containing a printable representation of an object. This is the same value yielded by conversions (reverse quotes). It is sometimes useful to be able to access this operation as an ordinary function. For many types, this function makes an attempt to return a string that would yield an object with the same value when passed to `eval()`.

`round`(x[, n])
  Return the floating point value x rounded to n digits after the decimal point. If n is omitted, it defaults to zero. The result is a floating point number. Values are rounded to the closest multiple of 10 to the power minus n; if two multiples are equally close, rounding is done away from 0 (so. for example, `round(0.5)` is `1.0` and `round(-0.5)` is `-1.0`).

`setattr`(object, name, value)
  This is the counterpart of `getattr()`. The arguments are an object, a string and an arbitrary value. The string may name an existing attribute or a new attribute. The function assigns the value to the attribute, provided the object allows it. For example, `setattr(x, 'foobar', 123)` is equivalent to `x.foobar = 123`.

`slice`([start,] stop[, step])
  Return a slice object representing the set of indices specified by `range(start, stop, step)`. The start and step arguments default to None. Slice objects have read-only data attributes `start`, `stop` and `step` which merely return the argument values (or their default). They have no other explicit functionality; however they are used by Numerical Python and other third party extensions. Slice objects are also generated when extended indexing syntax is used. For example: "`a[start:stop:step]`" or "`a[start:stop, i]`".

`str`(object)
  Return a string containing a nicely printable representation of an object. For strings, this returns the string itself. The difference with `repr(object)` is that `str(object)` does not always attempt to return a string that is acceptable to `eval()`; its goal is to return a printable string.

`tuple`([sequence])
  Return a tuple whose items are the same and in the same order as sequence's items. sequence may be a sequence, a container that supports iteration, or an iterator object. If sequence is already a tuple, it is returned unchanged. For instance, `tuple('abc')` returns returns `('a', 'b', 'c')` and `tuple([1, 2, 3])` returns `(1, 2, 3)`.

`type`(object)
  Return the type of an object. The return value is a type object. The standard module `types` defines names for all built-in types. For instance:

        >>> import types
        >>> if type(x) == types.StringType: print "It's a string"

`unichr`(i)
  Return the Unicode string of one character whose Unicode code is the integer i. For example, `unichr(97)` returns the string `u'a'`. This is the inverse of `ord()` for Unicode strings. The argument must be in the range [0..65535], inclusive. `ValueError` is raised otherwise. New in version 2.0.

`unicode`(object[, encoding[, errors]])
  Return the Unicode string version of object using one of the following modes:

  If encoding and/or errors are given, `unicode()` will decode the object which can either be an 8-bit string or a character buffer using the codec for encoding. The encoding parameter is a string giving the name of an encoding. Error handling is done according to errors; this specifies the treatment of characters which are invalid in the input encoding. If errors is `'strict'` (the default), a `ValueError` is raised on errors, while a value of `'ignore'` causes errors to be silently ignored, and a value of `'replace'` causes the official Unicode replacement character, `U+FFFD`, to be used to replace input characters which cannot be decoded. See also the `codecs` module.

  If no optional parameters are given, `unicode()` will mimic the behaviour of `str()` except that it returns Unicode strings instead of 8-bit strings. More precisely, if object is an Unicode string or subclass it will return a Unicode string without any additional decoding applied. For objects which provide a `__unicode__` method, it will call this method without arguments to create a Unicode string. For all other objects, the 8-bit string version or representation is requested and then converted to a Unicode string using the codec for the default encoding in `'strict'` mode. New in version 2.0.

`vars`([object])
  Without arguments, return a dictionary corresponding to the current local symbol table. With a module, class or class instance object as argument (or anything else that has a `__dict__` attribute), returns a dictionary corresponding to the object's symbol table. The returned dictionary should not be modified: the effects on the corresponding symbol table are undefined.2.4

`xrange`([start,] stop[, step])
  This function is very similar to `range()`, but returns an ``xrange object'' instead of a list. This is an opaque sequence type which yields the same values as the corresponding list, without actually storing them all simultaneously. The advantage of `xrange()` over `range()` is minimal (since `xrange()` still has to create the values when asked for them) except when a very large range is used on a memory-starved machine or when all of the range's elements are never used (such as when the loop is usually terminated with `break`).

`zip`(seq1, ...)
  This function returns a list of tuples, where the i-th tuple contains the i-th element from each of the argument sequences. At least one sequence is required, otherwise a `TypeError` is raised. The returned list is truncated in length to the length of the shortest argument sequence. When there are multiple argument sequences which are all of the same length, `zip()` is similar to `map()` with an initial argument of `None`. With a single sequence argument, it returns a list of 1-tuples. New in version 2.0.

#### Footnotes

... module.2.2
  It is used relatively rarely so does not warrant being made into a statement.
... used.2.3
  Specifying a buffer size currently has no effect on systems that don't have `setvbuf()`. The interface to specify the buffer size is not done using a method that calls `setvbuf()`, because that may dump core when called after any I/O has been performed, and there's no reliable way to determine whether this is the case.
... undefined.2.4
  In the current implementation, local variable bindings cannot normally be affected this way, but variables retrieved from other scopes (such as modules) can be. This may change.