Python String Processing Tricks and Tips

Stripping Whitepsace

s = '   This is a sentence with whitespace.       \n'

print('Strip leading whitespace: {}'.format(s.lstrip()))
print('Strip trailing whitespace: {}'.format(s.rstrip()))
print('Strip all whitespace: {}'.format(s.strip()))

Strip leading whitespace: This is a sentence with whitespace.       

Strip trailing whitespace:    This is a sentence with whitespace.
Strip all whitespace: This is a sentence with whitespace.

Striping unwanted characters

s = 'This is a sentence with unwanted characters.AAAAAAAA'
print('Strip unwanted characters: {}'.format(s.rstrip('A')))

Strip unwanted characters: This is a sentence with unwanted characters.

Spliting Strings

s = 'KDnuggets is a fantastic resource'

print(s.split())

['KDnuggets', 'is', 'a', 'fantastic', 'resource']

s = 'these,words,are,separated,by,comma'
print('\',\' separated split -> {}'.format(s.split(',')))

s = 'abacbdebfgbhhgbabddba'
print('\'b\' separated split -> {}'.format(s.split('b')))

',' separated split -> ['these', 'words', 'are', 'separated', 'by', 'comma']
'b' separated split -> ['a', 'ac', 'de', 'fg', 'hhg', 'a', 'dd', 'a']

Joining List Elements Into a String

s = ['KDnuggets', 'is', 'a', 'fantastic', 'resource']

print(' '.join(s))

KDnuggets is a fantastic resource

s = ['Eleven', 'Mike', 'Dustin', 'Lucas', 'Will']

print(' and '.join(s))

Eleven and Mike and Dustin and Lucas and Will

Reversing a String

s = 'KDnuggets'

print('The reverse of KDnuggets is {}'.format(s[::-1]))

The reverse of KDnuggets is: steggunDK

Converting Uppercase and Lowercase

s = 'KDnuggets'

print('\'KDnuggets\' as uppercase: {}'.format(s.upper()))
print('\'KDnuggets\' as lowercase: {}'.format(s.lower()))
print('\'KDnuggets\' as swapped case: {}'.format(s.swapcase()))

'KDnuggets' as uppercase: KDNUGGETS
'KDnuggets' as lowercase: kdnuggets
'KDnuggets' as swapped case: kdNUGGETS

Checking for String Membership

s1 = 'perpendicular'
s2 = 'pen'
s3 = 'pep'

print('\'pen\' in \'perpendicular\' -> {}'.format(s2 in s1))
print('\'pep\' in \'perpendicular\' -> {}'.format(s3 in s1))

'pen' in 'perpendicular' -> True
'pep' in 'perpendicular' -> False

s = 'Does this string contain a substring?'

print('\'string\' location -> {}'.format(s.find('string')))
print('\'spring\' location -> {}'.format(s.find('spring')))

'string' location -> 10
'spring' location -> -1

Replacing Substrings

s1 = 'The theory of data science is of the utmost importance.'
s2 = 'practice'

print('The new sentence: {}'.format(s1.replace('theory', s2)))

The new sentence: The practice of data science is of the utmost importance.

Combining the Output of Multiple Lists

countries = ['USA', 'Canada', 'UK', 'Australia']
cities = ['Washington', 'Ottawa', 'London', 'Canberra']

for x, y in zip(countries, cities):
  print('The capital of {} is {}.'.format(x, y))

The capital of USA is Washington.
The capital of Canada is Ottawa.
The capital of UK is London.
The capital of Australia is Canberra.

Checking for Anagrams

from collections import Counter
def is_anagram(s1, s2):
  return Counter(s1) == Counter(s2)

s1 = 'listen'
s2 = 'silent'
s3 = 'runner'
s4 = 'neuron'

print('\'listen\' is an anagram of \'silent\' -> {}'.format(is_anagram(s1, s2)))
print('\'runner\' is an anagram of \'neuron\' -> {}'.format(is_anagram(s3, s4)))

'listen' an anagram of 'silent' -> True
'runner' an anagram of 'neuron' -> False

Checking for Palindromes

def is_palindrome(s):
  reverse = s[::-1]
  if (s == reverse):
    return True
  return False

s1 = 'racecar'
s2 = 'hippopotamus'

print('\'racecar\' a palindrome -> {}'.format(is_palindrome(s1)))
print('\'hippopotamus\' a palindrome -> {}'.format(is_palindrome(s2)))

'racecar' is a palindrome -> True
'hippopotamus' is a palindrome -> False

Reference

• Tips and Tricks copied from kdnuggets