[已解决]怎么理解内置函数的*args和 **kwargs

wangwang123 · 发表于 2021-11-9 22:11:29

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def pop(self, *args, **kwargs): # real signature unknown
"""
Remove and return item at index (default last).
Raises IndexError if list is empty or index is out of range.
"""
pass

复制代码

这是我随便找的一个函数，我清楚pop的语法，既然在解释里面有*args（个数未知的位置形参）, 和**kwargs（个数未知关键字形参），是不是就可以理解：可以给pop函数传入两个以上的实参。我也试了一下，系统并没有给语法错误，但是运行会有bug.如下

TypeError: pop expected at most 1 argument, got 2

那我以后怎么知道一个函数，能传入几个参数呢？谢谢，现在不知道怎么理解*args了。

最佳答案

月排行榜 / 总排行榜

逃兵

2021-11-10 15:32:44

wangwang123 发表于 2021-11-10 15:20

class list(object)
| list(iterable=(), /)
|
| Built-in mutable sequence.
|
| If no argument is given, the constructor creates a new empty list.
| The argument must be an iterable if specified.
|
| Methods defined here:
|
| __add__(self, value, /)
| Return self+value.
|
| __contains__(self, key, /)
| Return key in self.
|
| __delitem__(self, key, /)
| Delete self[key].
|
| __eq__(self, value, /)
| Return self==value.
|
| __ge__(self, value, /)
| Return self>=value.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __getitem__(...)
| x.__getitem__(y) <==> x[y]
|
| __gt__(self, value, /)
| Return self>value.
|
| __iadd__(self, value, /)
| Implement self+=value.
|
| __imul__(self, value, /)
| Implement self*=value.
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __iter__(self, /)
| Implement iter(self).
|
| __le__(self, value, /)
| Return self<=value.
|
| __len__(self, /)
| Return len(self).
|
| __lt__(self, value, /)
| Return self<value.
|
| __mul__(self, value, /)
| Return self*value.
|
| __ne__(self, value, /)
| Return self!=value.
|
| __repr__(self, /)
| Return repr(self).
|
| __reversed__(self, /)
| Return a reverse iterator over the list.
|
| __rmul__(self, value, /)
| Return value*self.
|
| __setitem__(self, key, value, /)
| Set self[key] to value.
|
| __sizeof__(self, /)
| Return the size of the list in memory, in bytes.
|
| append(self, object, /)
| Append object to the end of the list.
|
| clear(self, /)
| Remove all items from list.
|
| copy(self, /)
| Return a shallow copy of the list.
|
| count(self, value, /)
| Return number of occurrences of value.
|
| extend(self, iterable, /)
| Extend list by appending elements from the iterable.
|
| index(self, value, start=0, stop=9223372036854775807, /)
| Return first index of value.
|
| Raises ValueError if the value is not present.
|
| insert(self, index, object, /)
| Insert object before index.
|
| pop(self, index=-1, /)
| Remove and return item at index (default last).
|
| Raises IndexError if list is empty or index is out of range.
|
| remove(self, value, /)
| Remove first occurrence of value.
|
| Raises ValueError if the value is not present.
|
| reverse(self, /)
| Reverse *IN PLACE*.
|
| sort(self, /, *, key=None, reverse=False)
| Stable sort *IN PLACE*.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __hash__ = None

复制代码

原函数list.pop默认一个参数，index=-1
你是要修改掉list类吗

跳转到最佳答案楼层

myqf123 · 发表于 2021-11-9 23:54:25

你这是某一个类里边的函数，正常这样写是可以传任意个参数的，但要看类__init__()这里接受几个参数，超出这个类的参数，你调用类的pop方法给任意个参数是不当的!

逃兵 · 发表于 2021-11-10 08:27:33

*args以元组方式储存传入的参数
**kwargs以字典方式储存传入的参数

def pop(*args, **kwargs):
print(args)
print(kwargs)
pop(1,2,3,4,a=5,b=6,c=7)

复制代码

wangwang123 · 发表于 2021-11-10 12:31:08

逃兵发表于 2021-11-10 08:27
*args以元组方式储存传入的参数
**kwargs以字典方式储存传入的参数

这个我能理解那函数解释里面有*arg 为什么pop函数只能输入一个值，不能pop(1,2），我的疑问在这。

逃兵 · 发表于 2021-11-10 13:16:52

wangwang123 发表于 2021-11-10 12:31
这个我能理解那函数解释里面有*arg 为什么pop函数只能输入一个值，不能pop(1,2），我的疑问在这。

把你运行报错的函数发一下

wangwang123 · 发表于 2021-11-10 15:20:51

逃兵发表于 2021-11-10 13:16
把你运行报错的函数发一下

lst = [1,2,3,4,5,6]
print(lst.pop(1,2))
运行错误：会说只能输入一个arg 所以就不知道怎么看这个函数定义了。

复制代码

逃兵 · 发表于 2021-11-10 15:32:44

wangwang123 发表于 2021-11-10 15:20

class list(object)
| list(iterable=(), /)
|
| Built-in mutable sequence.
|
| If no argument is given, the constructor creates a new empty list.
| The argument must be an iterable if specified.
|
| Methods defined here:
|
| __add__(self, value, /)
| Return self+value.
|
| __contains__(self, key, /)
| Return key in self.
|
| __delitem__(self, key, /)
| Delete self[key].
|
| __eq__(self, value, /)
| Return self==value.
|
| __ge__(self, value, /)
| Return self>=value.
|
| __getattribute__(self, name, /)
| Return getattr(self, name).
|
| __getitem__(...)
| x.__getitem__(y) <==> x[y]
|
| __gt__(self, value, /)
| Return self>value.
|
| __iadd__(self, value, /)
| Implement self+=value.
|
| __imul__(self, value, /)
| Implement self*=value.
|
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
|
| __iter__(self, /)
| Implement iter(self).
|
| __le__(self, value, /)
| Return self<=value.
|
| __len__(self, /)
| Return len(self).
|
| __lt__(self, value, /)
| Return self<value.
|
| __mul__(self, value, /)
| Return self*value.
|
| __ne__(self, value, /)
| Return self!=value.
|
| __repr__(self, /)
| Return repr(self).
|
| __reversed__(self, /)
| Return a reverse iterator over the list.
|
| __rmul__(self, value, /)
| Return value*self.
|
| __setitem__(self, key, value, /)
| Set self[key] to value.
|
| __sizeof__(self, /)
| Return the size of the list in memory, in bytes.
|
| append(self, object, /)
| Append object to the end of the list.
|
| clear(self, /)
| Remove all items from list.
|
| copy(self, /)
| Return a shallow copy of the list.
|
| count(self, value, /)
| Return number of occurrences of value.
|
| extend(self, iterable, /)
| Extend list by appending elements from the iterable.
|
| index(self, value, start=0, stop=9223372036854775807, /)
| Return first index of value.
|
| Raises ValueError if the value is not present.
|
| insert(self, index, object, /)
| Insert object before index.
|
| pop(self, index=-1, /)
| Remove and return item at index (default last).
|
| Raises IndexError if list is empty or index is out of range.
|
| remove(self, value, /)
| Remove first occurrence of value.
|
| Raises ValueError if the value is not present.
|
| reverse(self, /)
| Reverse *IN PLACE*.
|
| sort(self, /, *, key=None, reverse=False)
| Stable sort *IN PLACE*.
|
| ----------------------------------------------------------------------
| Static methods defined here:
|
| __new__(*args, **kwargs) from builtins.type
| Create and return a new object. See help(type) for accurate signature.
|
| ----------------------------------------------------------------------
| Data and other attributes defined here:
|
| __hash__ = None

复制代码

原函数list.pop默认一个参数，index=-1
你是要修改掉list类吗

wangwang123 · 发表于 2021-11-10 19:24:02

逃兵发表于 2021-11-10 15:32
原函数list.pop默认一个参数，index=-1
你是要修改掉list类吗

哈哈那肯定不是的我还没学到类我今天才看到类这块，所以知道自己问题出在哪了~谢谢

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[已解决]怎么理解内置函数的*args和 **kwargs

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