Python temporarily change letter to lower case -

i have list looks this:

separate=[['i','wnet','to','the','mal,'],['and','bouht','a','new','shirt.'],['what','did','you','do','todya?']]

i'm going run through program identify misspelled words , replace them correct word list of words in webster dictionary using uses lowercase letters. can temporarily change of letters lowercase in end return original upper , lower case words?

i know str.upper() , str.lower() , set.capitalize.

it seems want use str.capwords() inversely... want split list words(already done) , make capital letters lower case.

just use str.lower. return new string lower letter , keep original string unchanged. when loop through list such if string.lower() in adict:, use lower case compare , original string unchanged.

>>> = 'abc' >>> a.lower() 'abc' >>> 'abc'