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16.1 codec

The codecs module is used to handle different character encodings used with Unicode text I/O.

Low-level codec interface

A CodecInfo instance c has the following methods:

  • c.encode(s [, errors]). A stateless encoding function that encodes the Unicode string s and returns a tuple (bytes, length_consumed). bytes is an 8-bit string or byte-array containing the encoded data.
  • c.decode(bytes [, errors]). A stateless encoding function that decodes a byte string bytes and returns a tuple (s, length_consumed).
  • c.streamreader(bytestream [, errors]). Returns a StreamReader instance that is used to read encoded data.
  • c.streamwriter(bytestream [, errors]). Returns a StreamWriter instance that is used to write encoded data.
  • c.incrementalencoder([errors]). Returns an IncrementalEncoder instance that can be used to encode strings in multiple steps.
  • c.incrementaldecoder([errors]). Returns an IncrementalDecoder instance that can be used to decode byte strings in multiple steps.

I/O Related Functions

The codecs module provides a collection of high-level functions that are used to simplify I/O involving encoded text.

  • open(filename, mode[, encoding[, errors[, buffering]]]). Opens filename in the given mode and provides transparent data encoding/decoding according to the encoding specified in encoding.
  • EncodedFile(file, inputenc[, outputenc [, errors]]). A class that provides an encoding wrapper around an existing file object, file.

16.2 re

The re module is used to perform regular-expression pattern matching and replacement in strings. Both unicode and byte-strings are supported.

Functions

compile(str [, flags]) Compiles a regular-expression pattern string into a regular-expression object.

findall(pattern, string [,flags]) Returns a list of all nonoverlapping matches of pattern in string, including empty matches.

match(pattern, string [, flags]) Checks whether zero or more characters at the beginning of string match pattern.

search(pattern, string [, flags])

Searches string for the first match of pattern.

split(pattern, string [, maxsplit = 0])

Splits string by the occurrences of pattern.

sub(pattern, repl, string [, count = 0])

Replaces the leftmost nonoverlapping occurrences of pattern in string by using the replacement repl.

Regular Expression Objects

A compiled regular-expression object, r, created by the compile() function has the following methods and attributes.

  • r.pattern   The pattern string from which the regular expression object was compiled.
  • r.findall(string [, pos [, endpos]])   Identical to the findall() function.
  • r.split(string [, maxsplit = 0])   Identical to the split()`` function.   r.sub(repl, string [, count = 0])   Identical to the sub()` function.
  • r.search(string [, pos][, endpos])   Searches string for a match.
  • r.match(string [, pos][, endpos])   Checks whether zero or more characters at the beginning of string match.

Match Objects

The MatchObject instances returned by search() and match() contain information about the contents of groups as well as positional data about where matches occurred. A MatchObject instance, m, has the following methods and attributes:

  • m.group([group1, group2, ...]) Returns one or more subgroups of the match.
  • m.start([group]) m.end([group]) These two methods return the indices of the start and end of the substring matched by a group.

16.3 string

The string module contains a number of useful constants and functions for manipulating strings. It also contains classes for implementing new string formatters.

The str.format() method of strings is used to perform advanced string formatting operations.

The string module defines a class Formatter that can be used to implement your own customized formatting operation.

  • f.parse(format_string) A function that creates an iterator for parsing the contents of the format string format_string.
  • f.format(format_string, *args, **kwargs) Formats the string format_string.

The string module defines a new string type, Template, that simplifies certain string substitutions.

  • t.substitute(m [, **kwargs]) This method takes a mapping object, m (for example, a dictionary), or a list of keyword arguments and performs a keyword substitution on the string t.

16.4 struct

The struct module is used to convert data between Python and binary data structures (represented as Python byte strings).

Packing and Unpacking Functions

  • pack(fmt, v1, v2, ...) Packs the values v1, v2, and so on into a byte string according to the format string in fmt.
  • unpack(fmt, string)`` Unpacks the contents of a byte stringaccording to the format string infmt`.

Struct Objects

The struct module defines a class Struct that provides an alternative interface for packing and unpacking. Using this class is more efficient because the format string is only interpreted once.

# Packs values into a byte string
s.pack(v1, v2, ...)

# Unpacks values from a bytes string
s.unpack(bytes)

unicodedata

The unicodedata module provides access to the Unicode character database, which contains character properties for all Unicode characters.

Navigation

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