How to check if a key exists in a dictionary

How to check whether a key exists in the dictionary: You can use the has_key() method to determine, such as [arr.has_key("int")]. A dictionary is a mutable container model, and it can also store objects of any type.

Dictionary is another mutable container model and can store any type of object.

Each key-value (key=>value) pair in the dictionary is separated by a colon (:), each pair is separated by a comma (,), and the entire dictionary is included in curly braces ({}) , the format is as follows:

d = {key1 : value1, key2 : value2 }

Keys must be unique, but values ​​do not.

The value can be of any data type, but the key must be immutable, such as string, number or tuple.

The in method is used in python3

#判断字典中某个键是否存在
arr = {"int":"整数","float":"浮点","str":"字符串","list":"列表","tuple":"元组","dict":"字典","set":"集合"}
#使用 in 方法
if "int" in arr:
    print("存在")
if "float" in arr.keys():
    print("存在")
#判断键不存在
if "floats" not in arr:
    print("不存在")
if "floats" not in arr:
    print("不存在")

has_key() is not supported in python 3, but is supported in python2

#判断字典中某个键是否存在
arr = {"int":"整数","float":"浮点","str":"字符串","list":"列表","tuple":"元组","dict":"字典","set":"集合"}
#使用自带的has_key()
if(arr.has_key("int")):    
    print("存在")

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