This is all the code? List is redefined by you, when writing code, note variable naming don't function or keyword name repetition, > List=[1, 2, 3, 4] > C=(1, 2, 3, 4) > B=list (c) Traceback (the most recent call last) : The File "& lt; Pyshell# 13 & gt;" , line 1, in B=list (c) TypeError: 'list' object is not callable