Module Attributes
Python module has its attributes that describe it. Attributes perform some tasks or contain some information about the module. Some of the important attributes are explained below:
__name__
The __name__ attribute returns the name of the module. By default, the name of the file (excluding the extension.py) is the value of __name__ attribute.
>>> import math
>>> math.__name__
'math'
In the same way, it gives the name of your custom module.
>>> hello.__name__
'hello'
However, this can be modified by assigning different strings to this attribute. Change hello.py as shown below.
def SayHello(name):
print("Hi {}! How are you?".format(name))
__name__="SayHello"
And check the __name__ attribute now.
>>> import hello
>>> hello.__name__
'SayHello'
The value of the __name__ attribute is __main__ on the Python interactive shell.
>>> __name__
'__main__'
Sometimes, you will see below code in some modules:
if __name__=='__main__':
# do sth...
Let's modify the hello.py:
def SayHello(name):
print("Hi {}! How are you?".format(name))
if __name__=='__main__':
SayHello('Alice')
When we run the hello module file on the command line, the Python interpreter puts a special variable __name__ as a __main__, and if the hello module is imported elsewhere, the if condition will fail, so this if allows a module to execute some extra code when running from the command line, the most common being running the test.
$ python hello.py
Hi Alice! How are you?
If run hello.py from Python interactive shell and then import hello module:
$ python
Python 3.8.2 (default, Mar 25 2020, 11:22:43)
[Clang 4.0.1 (tags/RELEASE_401/final)] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import hello
>>>
As you can see, When importing, there is nothing to be printed, because the SayHello() function is not executed.
__doc__
The __doc__ attribute denotes the documentation string (docstring) line written in a module code.
>>> import math
>>> math.__doc__
'This module provides access to the mathematical functions\ndefined by the C standard.'
Consider the following script is saved as test.py module.
"""This is docstring of test module"""
def SayHello(name):
print("Hi {}! How are you?".format(name))
return
The __doc__ attribute will return a string defined at the beginning of the module code.
>>> import test
>>> test.__doc__
'This is docstring of test module'
__file__
__file__ is an optional attribute which holds the name and path of the module file from which it is loaded.
>>> import io
>>> io.__file__
'/Users/kimi/opt/anaconda3/lib/python3.8/io.py'
__dict__
The __dict__ attribute will return a dictionary object of module attributes, functions and other definitions and their respective values.
>>> import math
>>> math.__dict__
{'__name__': 'math',
'__doc__': 'This module provides access to the mathematical functions\ndefined by the C standard.',
'__package__': '',
'__loader__': <_frozen_importlib_external.ExtensionFileLoader at 0x7f78f0122ac0>,
'__spec__': ModuleSpec(name='math', loader=<_frozen_importlib_external.ExtensionFileLoader object at 0x7f78f0122ac0>, origin='/Users/kimi/opt/anaconda3/lib/python3.8/lib-dynload/math.cpython-38-darwin.so'),
'acos': <function math.acos(x, /)>,
'acosh': <function math.acosh(x, /)>,
'asin': <function math.asin(x, /)>,
'asinh': <function math.asinh(x, /)>,
'atan': <function math.atan(x, /)>,
'atan2': <function math.atan2(y, x, /)>,
'atanh': <function math.atanh(x, /)>,
'ceil': <function math.ceil(x, /)>,
'copysign': <function math.copysign(x, y, /)>,
'cos': <function math.cos(x, /)>,
'cosh': <function math.cosh(x, /)>,
'degrees': <function math.degrees(x, /)>,
'dist': <function math.dist(p, q, /)>,
'erf': <function math.erf(x, /)>,
'erfc': <function math.erfc(x, /)>,
'exp': <function math.exp(x, /)>,
'expm1': <function math.expm1(x, /)>,
'fabs': <function math.fabs(x, /)>,
'factorial': <function math.factorial(x, /)>,
'floor': <function math.floor(x, /)>,
'fmod': <function math.fmod(x, y, /)>,
'frexp': <function math.frexp(x, /)>,
'fsum': <function math.fsum(seq, /)>,
'gamma': <function math.gamma(x, /)>,
'gcd': <function math.gcd(x, y, /)>,
'hypot': <function math.hypot>,
'isclose': <function math.isclose(a, b, *, rel_tol=1e-09, abs_tol=0.0)>,
'isfinite': <function math.isfinite(x, /)>,
'isinf': <function math.isinf(x, /)>,
'isnan': <function math.isnan(x, /)>,
'isqrt': <function math.isqrt(n, /)>,
'ldexp': <function math.ldexp(x, i, /)>,
'lgamma': <function math.lgamma(x, /)>,
'log': <function math.log>,
'log1p': <function math.log1p(x, /)>,
'log10': <function math.log10(x, /)>,
'log2': <function math.log2(x, /)>,
'modf': <function math.modf(x, /)>,
'pow': <function math.pow(x, y, /)>,
'radians': <function math.radians(x, /)>,
'remainder': <function math.remainder(x, y, /)>,
'sin': <function math.sin(x, /)>,
'sinh': <function math.sinh(x, /)>,
'sqrt': <function math.sqrt(x, /)>,
'tan': <function math.tan(x, /)>,
'tanh': <function math.tanh(x, /)>,
'trunc': <function math.trunc(x, /)>,
'prod': <function math.prod(iterable, /, *, start=1)>,
'perm': <function math.perm(n, k=None, /)>,
'comb': <function math.comb(n, k, /)>,
'pi': 3.141592653589793,
'e': 2.718281828459045,
'tau': 6.283185307179586,
'inf': inf,
'nan': nan,
'__file__': '/Users/kimi/opt/anaconda3/lib/python3.8/lib-dynload/math.cpython-38-darwin.so'}
dir() is a built-in function that also returns the list of all attributes and functions in a module.
>>> dir(math)
['__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'comb',
'copysign', 'cos', 'cosh', 'degrees', 'dist', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'gcd',
'hypot', 'inf', 'isclose', 'isfinite', 'isinf', 'isnan', 'isqrt', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'log2', 'modf', 'nan', 'perm', 'pi', 'pow',
'prod', 'radians', 'remainder', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'tau', 'trunc']
Learn more about module attributes in Python Docs