The Python standard library includes may useful tools for a wide range of tasks.
This feature is sometimes called “batteries included”.
Python organizes libraries into modules that can be used in Python scripts.
There are also many third-party tools and packages that offer more specialized functionality.
import
StatementThe import
statement loads built-in and third party modules and can be used in various ways:
Explicit import (preserves the modules content in a namespace)
import math
math.cos(math.pi)
Explicit import by alias
import math as m
m.cos(m.pi)
Explicit import of module contents
from math import cos, pi
cos(pi)
Implicit import of module contents
from math import *
cos(pi)
A Python script can be treated as a module (imported into another Python program) or as a stand alone program.
A runnable script typically has a this statement
if __name__ == '__main__':
# statements that should not
# be executed when imported
# into another file
The code in the main block will not be executed when the file is imported.
os
and sys
: tools for interfacing with the operating system.
math
: mathematical functions and operations
itertools
: tools for constructing and interacting with iterators and generators.
random
: tools for generating pseudorandom numbers
json
and csv
: tools for reading file formats.
Python has modules that are not included in the standard library.
These modules can be imported like the standard library modules provided that they are installed.
Useful third-party modules:
numpy
: provides an efficient way to store and manipulate multi-dimensional dense arrays.
pandas
: provides a labeled interface to multi-dimensional data.
matplotlib
: provides a way to create scientific visualizations.