>>> a = [[None]*4] * 5 >>> b = [[None]*4 for _ in range(5)] >>> from pprint import pprint >>> pprint(a) >>> pprint(b) [[None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [[None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] >>> for i in range(5): >>> for j in range(4): >>> a[i][j]=str(i)+str(j) >>> pprint(a) >>> time.sleep(1) >>> print() [['00', None, None, None], ['00', None, None, None], ['00', None, None, None], ['00', None, None, None], ['00', None, None, None]] [['00', '01', None, None], ['00', '01', None, None], ['00', '01', None, None], ['00', '01', None, None], ['00', '01', None, None]] [['00', '01', '02', None], ['00', '01', '02', None], ['00', '01', '02', None], ['00', '01', '02', None], ['00', '01', '02', None]] [['00', '01', '02', '03'], ['00', '01', '02', '03'], ['00', '01', '02', '03'], ['00', '01', '02', '03'], ['00', '01', '02', '03']] [['10', '01', '02', '03'], ['10', '01', '02', '03'], ['10', '01', '02', '03'], ['10', '01', '02', '03'], ['10', '01', '02', '03']] [['10', '11', '02', '03'], ['10', '11', '02', '03'], ['10', '11', '02', '03'], ['10', '11', '02', '03'], ['10', '11', '02', '03']] [['10', '11', '12', '03'], ['10', '11', '12', '03'], ['10', '11', '12', '03'], ['10', '11', '12', '03'], ['10', '11', '12', '03']] [['10', '11', '12', '13'], ['10', '11', '12', '13'], ['10', '11', '12', '13'], ['10', '11', '12', '13'], ['10', '11', '12', '13']] [['20', '11', '12', '13'], ['20', '11', '12', '13'], ['20', '11', '12', '13'], ['20', '11', '12', '13'], ['20', '11', '12', '13']] [['20', '21', '12', '13'], ['20', '21', '12', '13'], ['20', '21', '12', '13'], ['20', '21', '12', '13'], ['20', '21', '12', '13']] [['20', '21', '22', '13'], ['20', '21', '22', '13'], ['20', '21', '22', '13'], ['20', '21', '22', '13'], ['20', '21', '22', '13']] [['20', '21', '22', '23'], ['20', '21', '22', '23'], ['20', '21', '22', '23'], ['20', '21', '22', '23'], ['20', '21', '22', '23']] [['30', '21', '22', '23'], ['30', '21', '22', '23'], ['30', '21', '22', '23'], ['30', '21', '22', '23'], ['30', '21', '22', '23']] [['30', '31', '22', '23'], ['30', '31', '22', '23'], ['30', '31', '22', '23'], ['30', '31', '22', '23'], ['30', '31', '22', '23']] [['30', '31', '32', '23'], ['30', '31', '32', '23'], ['30', '31', '32', '23'], ['30', '31', '32', '23'], ['30', '31', '32', '23']] [['30', '31', '32', '33'], ['30', '31', '32', '33'], ['30', '31', '32', '33'], ['30', '31', '32', '33'], ['30', '31', '32', '33']] [['40', '31', '32', '33'], ['40', '31', '32', '33'], ['40', '31', '32', '33'], ['40', '31', '32', '33'], ['40', '31', '32', '33']] [['40', '41', '32', '33'], ['40', '41', '32', '33'], ['40', '41', '32', '33'], ['40', '41', '32', '33'], ['40', '41', '32', '33']] [['40', '41', '42', '33'], ['40', '41', '42', '33'], ['40', '41', '42', '33'], ['40', '41', '42', '33'], ['40', '41', '42', '33']] [['40', '41', '42', '43'], ['40', '41', '42', '43'], ['40', '41', '42', '43'], ['40', '41', '42', '43'], ['40', '41', '42', '43']] >>> for i in range(5): >>> for j in range(4): >>> b[i][j]=str(i)+str(j) >>> pprint(b) >>> time.sleep(1) >>> print() [['00', None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', None], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], [None, None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', None, None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', None, None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', None], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], [None, None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', None, None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', None, None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', None], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], [None, None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', None, None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', None, None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', None], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', '33'], [None, None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', '33'], ['40', None, None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', '33'], ['40', '41', None, None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', '33'], ['40', '41', '42', None]] [['00', '01', '02', '03'], ['10', '11', '12', '13'], ['20', '21', '22', '23'], ['30', '31', '32', '33'], ['40', '41', '42', '43']]
