def to_weird_case(string):
    num = 0
    new_word = []
    for i in string:
        if num % 2 == 0:
            num += 1
            i.upper()
            new_word.append(i)
        else:
            num += 1
            i.lower()
            new_word.append(i)
    print(new_word)

to_weird_case('Test for test')

In [11]: s
Out[11]: 'Test for test'

In [12]: new = ''.join([x.lower() if x.isupper() else x.upper() for x in s])

In [13]: new
Out[13]: 'tEST FOR TEST'

In [37]: new = ''.join([c.upper() if i % 2 == 0 else c.lower() for i,c in enumerate(s)])

In [38]: new
Out[38]: 'TeSt fOr tEsT'

string = "Test for test"
new_string = ""
for i in string:
    if i.isupper():
        new_string += i.lower()
    else:
        new_string += i.upper()