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Measure the Elapsed Time in Python Represent enum Create a Countdown Timer Convert Bytes to a String

Introduction

Print Hello world!Add Two Numbers Find the Square Root Calculate the Area of a Triangle Solve Quadratic Equation Swap Two Variables Generate a Random Number Convert Kilometers to Miles Convert Celsius To Fahrenheit Print Output Without a Newline

Object Oriented

Get the Class Name of an Instance Differentiate Between type() and isinstance()

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Check if a Number is Positive, Negative or 0 Check if a Number is Odd or Even Check Leap Year Find the Largest Among Three Numbers Check Prime Number Print all Prime Numbers in an Interval Find the Factorial of a Number Display the multiplication Table Print the Fibonacci sequence Check Armstrong Number Find Armstrong Number in an Interval Find the Sum of Natural Numbers Create Pyramid Patterns Iterate Over Dictionaries Using for Loop Reverse a Number Compute the Power of a Number

Functions

Display Powers of 2 Using Anonymous Function Find Numbers Divisible by Another Number Convert Decimal to Binary, Octal and Hexadecimal Find ASCII Value of Character Find HCF or GCD Find LCM Find the Factors of a Number Make a Simple Calculator Shuffle Deck of Cards Display Calendar Display Fibonacci Sequence Using Recursion Find Sum of Natural Numbers Using Recursion Find Factorial of Number Using Recursion Convert Decimal to Binary Using Recursion Return Multiple Values From a Function

Native Datatypes

Add Two Matrices Transpose a Matrix Multiply Two Matrices Check Whether a String is Palindrome or Not Remove Punctuations From a String Sort Words in Alphabetic Order Illustrate Different Set Operations Count the Number of Each Vowel Merge Two Dictionaries Access Index of a List Using for Loop Flatten a Nested List Slice Lists Sort a Dictionary by Value Check If a List is Empty Concatenate Two Lists Check if a Key is Already Present in a Dictionary Split a List Into Evenly Sized Chunks Parse a String to a Float or Int Print Colored Text to the Terminal Convert String to Datetime Get the Last Element of the List Get a Substring of a String Randomly Select an Element From the List Check If a String Is a Number (Float)Count the Occurrence of an Item in a List Delete an Element From a Dictionary Create a Long Multiline String Convert Two Lists Into a Dictionary Trim Whitespace From a String Iterate Through Two Lists in Parallel Count the Number of Digits Present In a Number Check If Two Strings are Anagram Capitalize the First Character of a String Compute all the Permutation of the String Count the Number of Occurrence of a Character in String Remove Duplicate Element From a List

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Merge Mails Find the Size (Resolution) of an Image Find Hash of File Safely Create a Nested Directory Catch Multiple Exceptions in One Line Copy a File Python Program Read a File Line by Line Into a List Append to a File Extract Extension From the File Name Get the File Name From the File Path Get Line Count of a File Find All File with .txt Extension Present Inside a Directory Get File Creation and Modification Date Get the Full Path of the Current Working Directory Check the File Size

Python Program to Flatten a Nested List

To understand this example, you should have the knowledge of the following Python programming topics:

Example 1: Using List Comprehension


              
my_list = [[1], [2, 3], [4, 5, 6, 7]]

flat_list = [num for sublist in my_list for num in sublist]
print(flat_list)

Output


              
[1, 2, 3, 4, 5, 6, 7]

This is one of the simplest pythonic ways of flattening a list.

Using list comprehension access the sublist from my_list, then access each element of the sublist.
Each element num is stored in flat_list.

To learn more about list comprehension, visit Python List Comprehension.

Example 2: Using Nested for Loops (non pythonic way)


              
my_list = [[1], [2, 3], [4, 5, 6, 7]]

flat_list = []
for sublist in my_list:
    for num in sublist:
        flat_list.append(num)

print(flat_list)

Output


              
[1, 2, 3, 4, 5, 6, 7]

Create an empty list flat_list.
Access each element of the sublist using a nested loop and append that element to flat_list.

Example 3: Using itertools package


              
import itertools

my_list = [[1], [2, 3], [4, 5, 6, 7]]

flat_list = list(itertools.chain(*my_list))
print(flat_list)

Output


              
[1, 2, 3, 4, 5, 6, 7]

Using itertools module, we can create a flattened list.

chain() method from itertools module returns each element of each iterable (i.e. sub lists ).
list() converts those returned values into a list.

Example 4: Using sum()


              
my_list = [[1], [2, 3], [4, 5, 6, 7]]

flat_list = sum(my_list, [])
print(flat_list)

Output


              
[1, 2, 3, 4, 5, 6, 7]

Provide two arguments to the sum() method: my_list and an empty list (i.e. [ ]).
sum() combines my_list and [ ] to produce a flattened list.

Example 5: Using lambda and reduce()


              
from functools import reduce

my_list = [[1], [2, 3], [4, 5, 6, 7]]
print(reduce(lambda x, y: x+y, my_list))

Output


              
[1, 2, 3, 4, 5, 6, 7]

In the above example, reduce() applies the lambda function to all the elements of my_list.

To learn more about lambda expressions, visit Python Anonymous/Lambda Function.

Also Read:

Python Program to Concatenate Two Lists