Swap cases in a string

Question

I\'m trying to solve this challenge in hackerrank, which asks to convert all lowercase letters to uppercase letters and vice versa.

I attempt it with the following code:

Answer 1

Try this

def swap_case(s):
    l =[]
    str1 = ''
    for i in s:
        if i.isupper():

            l.append(i.lower())
        elif i.islower():
            l.append(i.upper())
        else:
            l.append(i)
    return (str1.join(l))
if __name__ == '__main__':
    s = input()
    result = swap_case(s)
    print(result)

Answer 2

As @Julien stated in comment upper and lower methods return a copy, and do not change the object itself. See this docs.

EDIT @aryamccarthy reminded me of already existing feature for this kind of task in python: swapcase() method. See more here. Note this also returns a copy of the string.

Answer 3

def swap_case(s):
    return s.swapcase()

#or you can use list comprehension 

def swap_case(s):
    new=[ch.lower() if ch.isupper() else ch.upper() for ch in s]
    new=''.join(new)
    return new

if __name__ == '__main__':
    s = input()
    result = swap_case(s)
    print(result)

Answer 4

def swap_case(s):
    list_s= list(s)
    for index,char in enumerate(list_s):
        if char == char.lower():
            list_s[index] =char.upper()
        else:
            list_s[index]= char.lower()
            s = ''.join(list_s)
    return s

string = 'HackerRank.com presents "Pythonist 2".'
print(swap_case(string))