# 12.20 `csv` -- CSV File Reading and Writing

New in version 2.3.

The so-called CSV (Comma Separated Values) format is the most common import and export format for spreadsheets and databases. There is no ``CSV standard'', so the format is operationally defined by the many applications which read and write it. The lack of a standard means that subtle differences often exist in the data produced and consumed by different applications. These differences can make it annoying to process CSV files from multiple sources. Still, while the delimiters and quoting characters vary, the overall format is similar enough that it is possible to write a single module which can efficiently manipulate such data, hiding the details of reading and writing the data from the programmer.

The `csv` module implements classes to read and write tabular data in CSV format. It allows programmers to say, ``write this data in the format preferred by Excel,'' or ``read data from this file which was generated by Excel,'' without knowing the precise details of the CSV format used by Excel. Programmers can also describe the CSV formats understood by other applications or define their own special-purpose CSV formats.

The `csv` module's `reader` and `writer` objects read and write sequences. Programmers can also read and write data in dictionary form using the `DictReader` and `DictWriter` classes.

Note: This version of the `csv` module doesn't support Unicode input. Also, there are currently some issues regarding ASCII NUL characters. Accordingly, all input should generally be printable ASCII to be safe. These restrictions will be removed in the future.

See Also:

PEP 305, CSV File API
  The Python Enhancement Proposal which proposed this addition to Python.

Subsections

- 12.20.1 Module Contents
- 12.20.2 Dialects and Formatting Parameters
- 12.20.3 Reader Objects
- 12.20.4 Writer Objects
- 12.20.5 Examples