Video link: https://www.youtube.com/watch?v=WfcozEiBIJU
In this video, we learned why modules are used and how we can import them in our program. We then learned to create custom modules with the help of examples.
Programs in the Video
A module is a file that contains Python code that we can use in our program.
There are several built-in functions like print(), input() and sum() that are readily available to us.
In addition to these functions, Python also has several functions that are defined inside a module which we can use after we import them.
Let's use one such module called math:
import math
number = 25
result = math.sqrt(number)
print(result)
print(math.pi)Output
5.0
3.141592653589793
Once we import a module, we can use everything inside it using the dot operator.
We imported math using the import statement and called its sqrt() function that calculates the square root of a number.
Also, the value of the constant pi is printed to the screen.
While importing a module, we can also rename it to a different name as per our needs.
Let's rename the math module to m:
import math as m
number = 25
result = m.sqrt(number)
print(result)
print(m.pi)Output
5.0
3.141592653589793
We get the same output as before.
When we import a module like in our previous examples, everything in the module is available to us.
However, if we only need to import a specific definition like a function or a constant, we can use the from..import statement.
from math import sqrt
num = sqrt(64)
print(num)Output
8.0
Here, only the sqrt function is imported from the math module.
When we use this syntax, instead of math.sqrt, we need to directly use the sqrt function.
We can also import multiple definitions from the module in a single line using this syntax:
from math import pi, sin, sqrt
value = sin(pi/2)
print(value)
num = sqrt(64)
print(num)Output
1.0
8.0
We can also use the from...import statement to import all definitions from a module using *:
from math import *
value = sin(pi/2)
print(value)
num = sqrt(64)
print(num)Output
1.0
8.0
Here, asterisk * means import everything.
Note: Importing every definition name with the asterisk symbol is a bad programming practice and you should try to avoid it in your code.
The math module comes with many more handy functions and constants.
We can list out all the things defined inside a module by using the dir() function:
import math
print(dir(math))Output
['__doc__', '__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']
As you can see, there are many other mathematical, trigonometric and logarithmic functions inside the math module.
The
mathmodule file comes when we install Python that's why we can import it directly. There are many popular modules that are not natively available for us to use. For example,numpyis a popular package that is used for scientific computing. To usenumpy, we must first install it.Similarly, you might have heard about
django. It's a popular framework used for creating web applications. It's also available only after we install it.
In Python, we can also create our own custom modules as per our needs. This helps us to keep our code organized.
Let's a module named calculator that will contain functions to perform arithmetic operations.
First, create a file named calculator.py in the same directory and add the following:
def add(a, b):
return a + b
def subtract(a, b):
return a - b
def multiply(a, b):
return a * b
def divide(a, b):
return a / b This file in itself is a module. Let's import this file from the main file.
In my main file:
import calculator
result1 = calculator.add(2, 3)
print(result1)
result2 = calculator.subtract(6, 3)
print(result2)
result3 = calculator.multiply(10, 3)
print(result3)
result4 = calculator.divide(6, 3)
print(result4)Output
5
3
30
2.0
In our example, we have only used functions and constants from a module. However a module may also contain classes or any other definitions.
Now, we can already sense how useful a module is. It helps us in better code management and improves the reusability of our code.