If some one can say what does happen with my pycharm, please, explain me my goof) Why does the list changes after assigning him a value? The code in comments) x = ['1.cad', '1.bat', '1.aa', '2.bat'] s = x print(s) for el in s: d = '' for e in range(len(el)): if ord(el[e]) in (range(97,123) or range(65,91)): d+=el[e] s[s.index(el)] = d s = sorted(s) a = [] print(x)