key and value in dictionary python code example

Example 1: how to get the key for a value in a dictionary in python

# function to return key for any value 
def get_key(val): 
    for key, value in my_dict.items(): 
         if val == value: 
             return key 
  
    return "key doesn't exist"
  
# Driver Code 
  
my_dict ={"java":100, "python":112, "c":11} 
  
print(get_key(100)) 
print(get_key(11))

Example 2: python dictionary

#Creating dictionaries
dict1 = {'color': 'blue', 'shape': 'square', 'volume':40}
dict2 = {'color': 'red', 'edges': 4, 'perimeter':15}

#Creating new pairs and updating old ones
dict1['area'] = 25 #{'color': 'blue', 'shape': 'square', 'volume': 40, 'area': 25}
dict2['perimeter'] = 20 #{'color': 'red', 'edges': 4, 'perimeter': 20}

#Accessing values through keys
print(dict1['shape'])

#You can also use get, which doesn't cause an exception when the key is not found
dict1.get('false_key') #returns None
dict1.get('false_key', "key not found") #returns the custom message that you wrote 

#Deleting pairs
dict1.pop('volume')

#Merging two dictionaries
dict1.update(dict2) #if a key exists in both, it takes the value of the second dict
dict1 #{'color': 'red', 'shape': 'square', 'area': 25, 'edges': 4, 'perimeter': 20}

#Getting only the values, keys or both (can be used in loops)
dict1.values() #dict_values(['red', 'square', 25, 4, 20])
dict1.keys() #dict_keys(['color', 'shape', 'area', 'edges', 'perimeter'])
dict1.items() 
#dict_items([('color', 'red'), ('shape', 'square'), ('area', 25), ('edges', 4), ('perimeter', 20)])

Example 3: for key value in dict python

a_dict = {"color": "blue", "fruit": "apple", "pet": "dog"}
for key in a_dict:
  print(key, '->', a_dict[key])

# Output:
# color -> blue
# fruit -> apple
# pet -> dog

Example 4: dictionary in python

thisdictionary = {'key':'value','key1':'value1'}
print(thisdictionary['key'])

Example 5: dict value python

obj = {0:"hello", 1:"there"}
print(obj[0])
print(obj[1])

print("\n\n\n\n\n")

for i in range(len(obj)):
  print(obj[i])