python赋值

最新推荐文章于 2025-12-22 13:59:14 发布
原创最新推荐文章于 2025-12-22 13:59:14 发布 · 126 阅读
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#python
本文探讨了Python中列表a和列表b通过双重循环进行动态赋值的区别，展示了如何使用str(i)+str(j)更新a和b的元素。a使用了嵌套循环，b则是在循环外部一次性赋值。
>>> 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']]