Python Standard Library

 

Standard Library

Built-in Functions

Built-in functions are Readily available for reuse.

Some of the built Functions are

1. print()

2. max()

3. min()

4. len()
   and many more..

Standard Library

Python provides several such useful values (constants), classes and functions.

This collection of predefined utilities is referred as the Python Standard Library

All these functionalities are organized into different modules.

• In Python context, any file containing a Python code is called a module
• These modules are further organized into folders known as packages

Different modules are:

1. collections

2. random

3. datetime

4. math and many more..

Working with Standard Library

To use a functionality defined in a module we need to import that module in our program.

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import module_name

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Math Module

math module provides us to access some common math functions and constants.

Code

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import math

print(math.factorial(5))

print(math.pi)

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Output

120

3.141592653589793

Importing module

Importing a module and giving it a new name (aliasing)

Code

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import math as m1

print(m1.factorial(5))

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Output

120

Importing from a Module

We can import just a specific definition from a module.

Code

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from math import factorial

print(factorial(5))

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Output

120

Aliasing Imports

We can also import a specific definition from a module and alias it

Code

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from math import factorial as fact

print(fact(5))

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Output

120

Random module

Randomness is useful in whenever uncertainty is required.

For example: Rolling a dice, flipping a coin, etc.,

random

module provides us utilities to create randomness.

Randint

randint()

is a function in random module which returns a random integer in the given interval.

Code

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import random

random_integer = random.randint(1, 10)

print(random_integer)

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Output

8

Choice

choice()

is a function in random module which returns a random element from the sequence.

Code

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import random

random_ele = random.choice(["A","B","C"])

print(random_ele)

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Output

B

To know more about Python Standard Library, go through the authentic python documentation - https://docs.python.org/3/library/

Map, Filter and Reduce

We worked with different sequences (list, tuples, etc.)

To simplify working with sequences we can use

map()

,

filter()

and

reduce()

functions.

Map

map()

applies a given function to each item of a sequence (list, tuple etc.) and returns a sequence of the results.

Example - 1

Code

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def square(n):

return n * n

numbers = [1, 2, 3, 4]

result = map(square, numbers)

numbers_square = list(result)

print(numbers_square)

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Output

[1, 4, 9, 16]

Example - 2

Code

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numbers = list(map(int, input().split()))

print(numbers)

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Input

1 2 3 4

Output

[1, 2, 3, 4]

Filter

filter()

method filters the elements of a given sequence based on the result of given function.

The function should return True/False

Code

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def is_positive_number(num):

return num > 0

list_a = [1, -2, 3, -4]

positive_nums = filter(is_positive_number, list_a)

print(list(positive_nums))

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Output

[1, 3]

Reduce

reduce()

function is defined in the functools module.

Code

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from functools import reduce

def sum_of_num(a, b):

return a+b

list_a = [1, 2, 3, 4]

sum_of_list = reduce(sum_of_num, list_a)

print(sum_of_list)

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Output

10