Python Tips and Tricks for Competitive Programming - GeeksforGeeks

19 Aug, 2021
Python Programming language makes everything easier and straightforward. Effective use of its built-in libraries can save a lot of time and help with faster submissions while doing Competitive Programming. Below are few such useful tricks that every Pythonist should have at their fingertips:
Converting a number into a List of digits using map() Function: 
Below is the implementation to convert a given number into a list of digits:
Python3
# Python program to convert a# number to a list of digits # Given numbern = 123456 # Stores the list of digitslis = list(map(int, str(n))) # Print the digitsprint(lis)
[1, 2, 3, 4, 5, 6]
 
Converting a sentence into a List of words using split() Function: Below is the implementation to convert a sentence into a list of words:
Python3
# Python program to convert# a sentence to a list of words # Given sentencesentence = "GeeksforGeeks is the computer science portal for geeks" # Convert the sentence# into a list of wordslis = list(sentence.split()) # Print the list of wordsprint(lis)
['GeeksforGeeks', 'is', 'the', 'computer', 'science', 'portal', 'for', 'geeks']
 
Take newline-separated integers as a List: Newline-separated input from the console can be taken in the form of a List using List Comprehension. Below is the implementation to take input of newline-separated integers as a list:
Python3
# Python program to take# newline-separated input# in the form of a list # Given inputn = int(input()) lis = [int(input()) for _ in range(n)]
Calculating GCD/HCF of two numbers: Gcd of two numbers can be computed in python using a built-in function gcd() offered by the Python Math Module.
Below is the implementation to demonstrate gcd() function: 
Python3
# Python program to demonstrate gcd() functionimport matha = 8b = 24 # Print the GCD of a and bprint(math.gcd(a, b))
8
 
Print permutations of array: All permutations of an array can be efficiently generated using built-in permutations() method from itertools package. This method takes a List as input and returns an object List of Tuples that contains all permutations.
Below is the implementation of the approach:
Python3
# Python program to print all# permutations using library functionfrom itertools import permutations # Get all permutations of [1, 2, 3]perm = permutations([1, 2, 3]) # Print the obtained permutationsfor i in list(perm):    print (i)
(1, 2, 3)
(1, 3, 2)
(2, 1, 3)
(2, 3, 1)
(3, 1, 2)
(3, 2, 1)
 
Printing a string multiple times without Loop: Below is the implementation to print a string multiple times without loop using string multiplication technique:
Python3
# Python program to print# a string given number of times # Given stringstr ="India" # Print the string 2 timesprint(str * 2)
IndiaIndia
 
To print a list with spaces without loop: A list can be printed without running the loop by using the * operator in Python.
Below is the implementation to print a list with spaces without loop: 
Python3
# Python program to print a list with spaces without looplis = [1, 2, 3, 4] # Printing list elements with spacesprint(*lis)
1 2 3 4
 
Convert binary string to decimal: A binary string can be converted to its decimal equivalent using built-in int() function.
Below is the implementation of the above approach: 
Python3
# Python program to convert a# binary string to its decimal# equivalent using int() function # Given stringbinary = "1010" # Print decimal equivalentprint(int(binary, 2))
10
To print sorted list with spaces: Sorting any sequence is very easy in Python using a built-in method sorted() and using * symbol to print list with spaces. Sorted() sorts any sequence (list, tuple) and always returns a list with the elements in a sorted manner, without modifying the original sequence.
Below is the implementation to print a sorted list with spaces: 
Python3
# Python program to print a sorted list with# spaces using sorted() functionlis = [6, 2, 7, 3, 4] # Print the sorted sequenceprint(*sorted(lis))
2 3 4 6 7
 
To find common elements in two arrays: The common elements in 2 arrays/lists can be done in a much simpler way using sets. The intersection() function in Python gives the common elements in both arrays/lists.
Below is the implementation to demonstrate intersection() function:
Python3
# Python program to print common elements in# both the list using intersection() functionarray1 = [4, 5, 6, 7, 8]array2 = [3, 4, 5, 1, 72] # Print the common elementsprint(set(array1).intersection(set(array2)))
{4, 5}
 
abhishek0719kadiyan
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