Adding a prefix to each key name in a Python dictionary

In this article, we will understand how to add a prefix to each key name in a Python dictionary. Dictionaries in Python are collections of unordered items stored in the form of key-value pairs inside curly braces like this ?

Dictionary = {key: value,?.}

Our goal is to add a prefix (i.e., a word or character added at the beginning of another word) to each key name of the dictionary in Python.

Suppose a key in a dictionary is "name", on adding the prefix "company_" to it, the key becomes "company_name".

For example ?

#Input dictionary:
Dictionary = {'name': 'Tutorialspoint', 'location': 'Hyderabad'}

#Prefix to add
Prefix = 'Company_'

#Output dictionary
New Dictionary = {'Company_name': 'Tutorialspoint', 'Company_location': 'Hyderabad'}

Adding Prefix to Key Name in Python Dictionary

We can add a prefix to keys name of a dictionary in Python using the following approaches ?

• Using a For loop
• Using Dictionary Comprehension
• Using map() function and "+" operator
• Using a Function and Dictionary operator

Let us go through this all one by one ?

Using a For loop

The for loop in Python is used to traverse a sequence of items. Using this, we can add a prefix to the dictionary keys by looping through them and their associated values. Then, we can insert the updated key-value pairs to an empty dictionary.

Example

The following program prints the dictionary key with a prefix using a for loop in Python.

# Initializing a dictionary
D = {"name": "Tutorialspoint", "location": "Hyderabad"}

# Intializing an empty dictionary
new_dict = {}

# Looping over each key in dictionary
# and adding prefix to them
for k, v in D.items():
    new_dict[f"Company_{k}"] = v

# Printing the new dictionary
print(new_dict)

Output

{'Company_name': 'Tutorialspoint', 'Company_location': 'Hyderabad'}

Using Dictionary Comprehension

The dictionary comprehension (or dict comprehension) is used to create a dictionary in Python from key-value pairs of a provided iterable. We can perform an operation on each key-value pair of the iterable and store the resulting values as a dictionary.

To add a prefix to a dictionary key name, we need to pass it as an iterable to a dictionary comprehension. It will create a new dictionary using the original keys and values, with the prefix added to the key names.

Example

The following program prints the dictionary key with a prefix using dictionary comprehension in Python.

# Initializing a dictionary
D = {"name": "Tutorialspoint", "location": "Hyderabad"}

# Looping over each key in dictionary
# and adding a prefix to them
new_dict = {f"Company_{k}": v for k, v in D.items()}

# Printing the new dictionary
print(new_dict)

Output

{'Company_name': 'Tutorialspoint', 'Company_location': 'Hyderabad'}

Using map() Function with "+" Operator

The map() function in Python accepts two arguments, a function and an iterable. It returns a new iterable object by applying the specified function to each item of a given iterable.

To add a prefix to key names of a dictionary, we need to pass the dictionary as an iterable and a function to the map() function. This function concatenates the prefix with key name in a dictionary using the '+' operator.

Example

The following program prints the dictionary key with a prefix using a map() function and "+" operator in Python.

# Initializing a dictionary
D = {"name": "Tutorialspoint", "location": "Hyderabad"}

#Adding prefix to dictianary keys
new_dict = dict(map(lambda item: ("Comapny_" + item[0], item[1]), D.items()))

# Printing the new dictionary
print(new_dict)

Output

{'Comapny_name': 'Tutorialspoint', 'Comapny_location': 'Hyderabad'}

Using a Function and Dictionary Comprehension

We can add a prefix to dictionary keys in Python using a function. This function takes a dictionary and its keys as arguments and returns a new dictionary having prefix with each key names using dictionary comprehension and concatenation("+" operator).

Example

The following program prints the dictionary key with a prefix using a function and dictionary comprehension in Python.

# Initializing a dictionary
D = {"name": "Tutorialspoint", "location": "Hyderabad"}

#Defining a function
def new_dict(D, prefix):
   return {prefix + k: v for k, v in D.items()}

# Calling function and
# Printing the new dictionary
print(new_dict(D,"Company_"))

Output

{'Company_name': 'Tutorialspoint', 'Company_location': 'Hyderabad'}

Conclusion

In this article, we have seen multiple approaches for adding a prefix to each key name in a Python dictionary. The dictionary comprehension and the map() function are a concise way that allows us to achieve this task using a single line of statement, whereas for loop performs the taks step by step.