This article describes how to check if a key, value, or key-value pair exists in a dictionary (dict) in Python. - Check if a key exists in a dictionary:
in operator - Check if a value exists in a dictionary:
in operator, values() - Check if a key-value pair exists in a dictionary:
in operator, print(d['key1'])
# val1
0
The values() and print(d['key1'])
# val1
0 methods are also used to iterate a dictionary with print(d['key1'])
# val1
3 loop. See the following article.- Iterate dictionary (key and value) with for loop in Python
Sponsored Link Check if a key exists in a dictionary: in operatorUsing the in operator for a dictionary object itself returns if a key exists, i.e., if a dictionary has/contains a key. Use print(d['key1'])
# val1
6 to check if a key does not exist in a dictionary.d = {'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}
print('key1' in d)
# True
print('val1' in d)
# False
print('key4' not in d)
# True
source: The same is true if you use the print(d['key1'])
# val1
7 method instead of the dictionary object itself. In the case of the above example, the same result is returned by print(d['key1'])
# val1
8.The print(d['key1'])
# val1
9 method was provided in Python 2, but was removed in Python 3.To get the value for the key, use # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
0.print(d['key1'])
# val1
source: # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
0 raises an error when the key does not exist, but the # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
2 method returns a specified value (default is # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
3) if the key does not exist.- Get value from dictionary by key with get() in Python
# print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
source: You can also add a new item with # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
4. The value is overwritten for an existing key. If you want to add an item with a new value only for a new key without changing the value for an existing key, use the # print(d['key4'])
# KeyError: 'key4'
print(d.get('key4'))
# None
5 method. See the following article.- Add an item only when the key does not exist in dict in Python (setdefault())
Check if a value exists in a dictionary: in operator, values()To check if a value exists in a dictionary, i.e., if a dictionary has/contains a value, use the in operator and the values() method. Use print(d['key1'])
# val1
6 to check if a value does not exist in a dictionary.print('val1' in d.values())
# True
print('val4' not in d.values())
# True
source: See the following article for how to get the key from the value. - Get key from value in dictionary in Python
Sponsored Link Check if a key-value pair exists in a dictionary: in operator, print(d['key1'])
# val1
0To check if a key-value pair exists in a dictionary, i.e., if a dictionary has/contains a pair, use the in operator and the print(d['key1'])
# val1
0 method. Specify a tuple print('val1' in d.values())
# True
print('val4' not in d.values())
# True
5. Use print(d['key1'])
# val1
6 to check if a pair does not exist in a dictionary. | 
