Given a list of strings, write a Python program to convert all strings from lowercase/uppercase to uppercase/lowercase.
Input : ['GeEk', 'FOR', 'gEEKS'] Output: ['geek', 'for', 'Lazyroar'] Input : ['fun', 'Foo', 'BaR'] Output: ['FUN', 'FOO', 'BAR']
Method #1: Convert Uppercase to Lowercase using map function
Python3
# Python code to convert all string# from uppercase to lowercase.# Using map functionout = map(lambda x:x.lower(), ['GeEk', 'FOR', 'gEEKS'])# Converting it into listoutput = list(out)# printing outputprint(output) |
['geek', 'for', 'Lazyroar']
Time complexity: O(n), where n is the length of the input list.
Auxiliary space: O(n), where n is the length of the output list.
Method #2: Convert Lowercase to Uppercase using List comprehension
Python3
# Python code to convert all string# from uppercase to lowercase.# Initialisationinput = ['fun', 'Foo', 'BaR']# Convertinglst = [x.upper() for x in input]# printing outputprint(lst) |
['FUN', 'FOO', 'BAR']
Time complexity: O(n), where n is the number of elements in the input list.
Auxiliary space: O(n), where n is the number of elements in the input list, as a new list is created to store the converted strings.
Method #3: Using enumerate function
Python3
lst = ['Foo', 'fOO', 'geeKs']lst = [i.lower() for a,i in enumerate(lst)]print(lst) |
['foo', 'foo', 'Lazyroar']
Time complexity: O(n), where n is the length of the list.
Auxiliary space: O(n), as a new list is created to store the lowercase version of each string in the original list.
Method #4: Using casefold()
The approach is to use the str.casefold() method. This method is similar to the str.lower() method, but it is more aggressive in converting the string to a lowercase representation. It is particularly useful for handling case conversions involving non-ASCII characters, such as those found in the German language.
Here is an example of using str.casefold() to convert a list of strings to lowercase:
Python3
input = ['GeEk', 'FOR', 'gEEKS']output = [s.casefold() for s in input]print(output)# Output: ['geek', 'for', 'Lazyroar']#This code is contributed by Edula Vinay Kumar Reddy |
['geek', 'for', 'Lazyroar']
Time complexity: O(n), where n is the length of the input list.
Auxiliary space: O(n), where n is the length of the output list.
Method 5: Using the lower()
Python3
input = ['fun', 'Foo', 'BaR']lst = [x.lower() for x in input]print(lst) |
['fun', 'foo', 'bar']
Time Complexity: O(n)
Auxiliary Space: O(n), where n is length of list.
Method #6: Using a for loop
Convert uppercase letters to lowercase by using a for loop to iterate through each character in the string, and then using the lower() function to convert the uppercase letter to lowercase.
Python3
# Python code to convert all string# from uppercase to lowercase.# Using a for loopstring = 'GeEk FOR gEEKS'output = ''for char in string: if char.isupper(): output += char.lower() else: output += char# printing outputprint(output) |
geek for Lazyroar
Time complexity: O(n), where n is the length of the input string. This is because the for loop iterates through each character in the string exactly once.
Auxiliary space: O(n), as we are creating a new string (output) to store the lowercase version of the input string.
