Standard Library. While The Python Language Reference describes the exact syntax and semantics of the Python language, this library reference manual describes the standard library that is distributed with Python. It also describes some of the optional components that are commonly included in Python distributions. Python’s standard library is very extensive, offering a wide range of facilities as indicated by the long table of contents listed below. The library contains built-in modules (written in C) that provide access to system functionality such as file I/O that would otherwise be inaccessible to Python programmers, as well as modules written in Python that provide standardized solutions for many problems that occur in everyday programming.
Some of these modules are explicitly designed to encourage and enhance the portability of Python programs by abstracting away platform-specifics into platform-neutral APIs. 2. Built-in Functions. Open file and return a corresponding file object. If the file cannot be opened, an OSError is raised. See Reading and Writing Files for more examples of how to use this function. file is a path-like object giving the pathname (absolute or relative to the current working directory) of the file to be opened or an integer file descriptor of the file to be wrapped.
(If a file descriptor is given, it is closed when the returned I/O object is closed unless closefd is set to False.) mode is an optional string that specifies the mode in which the file is opened. The default mode is 'r' (open for reading text, a synonym of 'rt'). As mentioned in the Overview, Python distinguishes between binary and text I/O. Note Python doesn’t depend on the underlying operating system’s notion of text files; all the processing is done by Python itself, and is therefore platform-independent. buffering is an optional integer used to set the buffering policy. The newly created file is non-inheritable. 6.2. re — Regular expression operations — Python v3.2.2 documentation. This module provides regular expression matching operations similar to those found in Perl.
Both patterns and strings to be searched can be Unicode strings (str) as well as 8-bit strings (bytes). However, Unicode strings and 8-bit strings cannot be mixed: that is, you cannot match a Unicode string with a bytes pattern or vice-versa; similarly, when asking for a substitution, the replacement string must be of the same type as both the pattern and the search string. Regular expressions use the backslash character ('\') to indicate special forms or to allow special characters to be used without invoking their special meaning. This collides with Python’s usage of the same character for the same purpose in string literals; for example, to match a literal backslash, one might have to write '\\\\' as the pattern string, because the regular expression must be \\, and each backslash must be expressed as \\ inside a regular Python string literal. Regular Expression Syntax (Dot.) (Caret.)
{m} {m,n} (? Overview. Coding style, coding style, CODING STYLE!!!! Besides the while statement just introduced, Python knows the usual control flow statements known from other languages, with some twists. 4.1. if Statements Perhaps the most well-known statement type is the if statement. For example: >>> x = int(input("Please enter an integer: "))Please enter an integer: 42>>> if x < 0:... x = 0... print('Negative changed to zero')... elif x == 0:... print('Zero')... elif x == 1:... print('Single')... else:... print('More')...More There can be zero or more elif parts, and the else part is optional. 4.2. for Statements The for statement in Python differs a bit from what you may be used to in C or Pascal.
>>> # Measure some strings:... words = ['cat', 'window', 'defenestrate']>>> for w in words:... print(w, len(w))...cat 3window 6defenestrate 12 If you need to modify the sequence you are iterating over while inside the loop (for example to duplicate selected items), it is recommended that you first make a copy. 4.3. >>> for i in range(5):... print(i)...01234.