python - 将值解压到变量中或无(ValueError : not enough values to unpack)

Question

iterable应该如何被解包成数量不匹配的变量？

值太多:

>>> one,two = [1,2,3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: too many values to unpack (expected 2)

可以忽略

>>> one,two,*_ = [1,2,3,4]  
>>> 

注意:“extended iterable unpacking ”仅自 Python 3 起。关于underscore .

数据太少/变量较多的相反情况如何:

>>> one,two,three = [1,2]   
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not enough values to unpack (expected 3, got 2)
>>>

进行处理，特别是为剩余的变量分配 None (或其他值)？

类似这样的事情:

>>> one,two,three = [1,2] or None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: not enough values to unpack (expected 3, got 2)
>>>

<小时/> https://stackoverflow.com/a/8857846/1619432建议扩大列表:

>>> one,two,three = [1,2] + [None]*(3-2)
>>> one   
1
>>> two
2
>>> three
>>>

Answer 1

您可以使用以下方法将序列解压缩为三个变量:

one, two, *three = [1,2]

此时，two 将是一个空列表。然后，您可以使用 or 检查 3 是否为空，将 two 分配给 None。

three = three or None