Check whether given Key already exists in a Python Dictionary
Given a dictionary in Python, write a Python program to check whether a given key already exists in a dictionary. If present, print “Present” and the value of the key. Otherwise print “Not present”.
Examples:
Input : {'a': 100, 'b':200, 'c':300}, key = b Output : Present, value = 200 Input : {'x': 25, 'y':18, 'z':45}, key = w Output : Not present
Approach #1 : Using Inbuilt method keys()
keys()
method returns a list of all the available keys in the dictionary. With the Inbuilt method keys()
, use if statement and the ‘in’ operator to check if the key is present in the dictionary or not.
# Python3 Program to check whether a # given key already exists in a dictionary. # Function to print sum def checkKey( dict , key): if key in dict .keys(): print ( "Present, " , end = " " ) print ( "value =" , dict [key]) else : print ( "Not present" ) # Driver Code dict = { 'a' : 100 , 'b' : 200 , 'c' : 300 } key = 'b' checkKey( dict , key) key = 'w' checkKey( dict , key) |
Output:
Present, value = 200 Not present
Approach #2 : Using if
and in
This method simply uses if
statement to check whether the given key exist in the dictionary.
# Python3 Program to check whether a # given key already exists in a dictionary. # Function to print sum def checkKey( dict , key): if key in dict : print ( "Present, " , end = " " ) print ( "value =" , dict [key]) else : print ( "Not present" ) # Driver Code dict = { 'a' : 100 , 'b' : 200 , 'c' : 300 } key = 'b' checkKey( dict , key) key = 'w' checkKey( dict , key) |
Output:
Present, value = 200 Not present
Approach #3 : Using Inbuilt method has_key()
has_key()
method returns true if a given key is available in the dictionary, otherwise it returns a false. With the Inbuilt method has_key()
, use if statement to check if the key is present in the dictionary or not.
Note – has_keys()
method has been removed from Python3 version. Therefore, it can be used in Python2 only.
# Python3 Program to check whether a # given key already exists in a dictionary. # Function to print sum def checkKey( dict , key): if dict .has_key(key): print "Present, value =" , dict [key] else : print "Not present" # Driver Function dict = { 'a' : 100 , 'b' : 200 , 'c' : 300 } key = 'b' checkKey( dict , key) key = 'w' checkKey( dict , key) |
Output:
Present, value = 200 Not present