大连手机网站建设,常州网站制作公司有哪些,网站登录界面 psd,网络营销分类Python语言为几乎所有容器(无论是列表容器还是集合容器)指定了pop()。这篇特别的文章着重说明Python词典提供的pop()方法。这种方法对于经常处理字典的程序员很有用。
用法#xff1a;dict.pop(key, def)
参数#xff1a;
key:必须返回并删除其键值对的键。
def:如果指定的键…Python语言为几乎所有容器(无论是列表容器还是集合容器)指定了pop()。这篇特别的文章着重说明Python词典提供的pop()方法。这种方法对于经常处理字典的程序员很有用。
用法dict.pop(key, def)
参数
key:必须返回并删除其键值对的键。
def:如果指定的键不存在则返回的默认值。
返回
如果存在键则与已删除键/值对关联的值。
如果不存在 key 则指定为默认值。
KeyError如果不存在 key 且未指定默认值。
代码1演示工作pop()当存在 key 时。
# Python 3 code to demonstrate
# working of pop()
# initializing dictionary
test_dict { Nikhil :7, Akshat :1, Akash :2 }
# Printing initial dict
print (The dictionary before deletion: str(test_dict))
# using pop to return and remove key-value pair.
pop_ele test_dict.pop(Akash)
# Printing the value associated to popped key
print (Value associated to poppped key is: str(pop_ele))
# Printing dictionary after deletion
print (Dictionary after deletion is: str(test_dict))
输出
The dictionary before deletion:{Nikhil:7, Akshat:1, Akash:2}
Value associated to poppped key is:2
Dictionary after deletion is:{Nikhil:7, Akshat:1}
的行为pop()当字典中不存在该键时功能会有所不同。在这种情况下如果没有提供默认值它将返回提供的默认值或KeyError。
代码2演示pop()在没有 key 的情况下的工作
# Python 3 code to demonstrate
# working of pop() without key
# initializing dictionary
test_dict { Nikhil :7, Akshat :1, Akash :2 }
# Printing initial dict
print (The dictionary before deletion: str(test_dict))
# using pop to return and remove key-value pair
# provided default
pop_ele test_dict.pop(Manjeet, 4)
# Printing the value associated to popped key
# Prints 4
print (Value associated to poppped key is: str(pop_ele))
# using pop to return and remove key-value pair
# not provided default
pop_ele test_dict.pop(Manjeet)
# Printing the value associated to popped key
# KeyError
print (Value associated to poppped key is: str(pop_ele))
输出
The dictionary before deletion:{Nikhil:7, Akshat:1, Akash:2}
Value associated to poppped key is:4
Traceback (most recent call last):
File main.py, line 20, in
pop_ele test_dict.pop(Manjeet)
KeyError:Manjeet
