Create Dictionary With Predefined Keys in Python

This tutorial will discuss about unique ways to create dictionary with predefined keys in Python.

Table Of Contents

Create Python Dictionary with Predefined Keys & a default value

Suppose we have a list of predefined keys,

keys = ['Ritika', 'Smriti', 'Mathew', 'Justin']

We want to create a dictionary from these keys.

Dictionary should have all the keys specified in the list. But as a dictionary contains this key-value pairs, therefore value of each key will be a default value.

For that we will use the fromkeys() method of the dictionary to create a dictionary. In this method, we will pass the list of keys as the first argument and the default value is the second argument. It will return as a dictionary initialised with key value pairs, where keys will be picked the given list, and each key will have the same specified default value.

Let’s see the complete example,

# A List of Keys
keys = ['Ritika', 'Smriti', 'Mathew', 'Justin']

# Default value for each Key
value = 10

# Create a Dictionary with the keys from list and a default value
students = dict.fromkeys(keys, value)

# Print the Dictionary
print(students)

Output

{'Ritika': 10, 'Smriti': 10, 'Mathew': 10, 'Justin': 10}

Create Python Dictionary with Predefined Keys & auto incremental value

Suppose we have a list of predefined keys,

keys = ['Ritika', 'Smriti', 'Mathew', 'Justin']

We want to create a dictionary from these keys, but the value of each key should be an integer value. Also the values should be the incrementing integer value in the dictionary. Like,

• For the first Key, the value should be 1.
• For the second Key, the value should be 2.
• For the third Key, the value should be 3.
• For the Nth Key, the value should be N.

Using a Dictionary Comprehension, we will iterate from index zero till N. Where N is the number of keys in the list. During iteration, for each index we will pick the ith Key from the list and add a key-value pair in the dictionary using the Dictionary Comprehension

Let’s see the complete example,

# A List of Keys
keys = ['Ritika', 'Smriti', 'Mathew', 'Justin']

# Create a dictionary with incrementing
# values for the keys from list
students = {keys[i]: i+1 for i in range(len(keys))}

# Print the Dictionary
print(students)

Output

{'Ritika': 1, 'Smriti': 2, 'Mathew': 3, 'Justin': 4}

Summary

We learned how to create a Dictionary With Predefined Keys in Python.