How to read Dictionary from File in Python?

Last Updated : 20 Aug, 2020

A Dictionary in Python is collection of key-value pairs, where key is always unique and oftenly we need to store a dictionary and read it back again.

We can read a dictionary from a flie in 3 ways:

Using the json.loads() method : Converts the string of valid dictionary into json form.
Using the ast.literal_eval() method : Function safer than the eval function and can be used for interconversion of all data types other than dictionary as well.
Using the pickle.loads() method : We can also use Pickle module if the file is serialized into a character stream.

Input File:

Method 1 : Using json.loads() :

# importing the module
import json
  
# reading the data from the file
with open('dictionary.txt') as f:
    data = f.read()
  
print("Data type before reconstruction : ", type(data))
      
# reconstructing the data as a dictionary
js = json.loads(data)
  
print("Data type after reconstruction : ", type(js))
print(js)

Output :

Data type before reconstruction :  <class 'str'>
Data type after reconstruction :  <class 'dict'>
{'Name': 'John', 'Age': 21, 'Id': 28}

Method 2 : Using ast.literal_eval() :

# importing the module
import ast
  
# reading the data from the file
with open('dictionary.txt') as f:
    data = f.read()
  
print("Data type before reconstruction : ", type(data))
      
# reconstructing the data as a dictionary
d = ast.literal_eval(data)
  
print("Data type after reconstruction : ", type(d))
print(d)

Output :

Data type before reconstruction :  <class 'str'>
Data type after reconstruction :  <class 'dict'>
{'Name': 'John', 'Age': 21, 'Id': 28}

Method 3 : We can use the Pickle module for the same purpose, but this method will only work if the file is serialized into a character stream and not in text format. To know more about Pickling in Python click here

# importing the module
import pickle
  
# opening file in write mode (binary)
file = open("dictionary.txt", "wb")
  
my_dict = {"Name": "John",
           "Age": 21,
           "Id": 28}
  
# serializing dictionary 
pickle.dump(my_dict, file)
  
# closing the file
file.close()
  
# reading the data from the file
with open('dictionary.txt', 'rb') as handle:
    data = handle.read()
  
print("Data type before reconstruction : ", type(data))
  
# reconstructing the data as dictionary
d = pickle.loads(data)
  
print("Data type after reconstruction : ", type(d))
print(d)

Output :

Data type before reconstruction :  <class 'bytes'>
Data type after reconstruction :  <class 'dict'>
{'Name': 'John', 'Age': 21, 'Id': 28}

Attention geek! Strengthen your foundations with the Python Programming Foundation Course and learn the basics.

To begin with, your interview preparations Enhance your Data Structures concepts with the Python DS Course. And to begin with your Machine Learning Journey, join the Machine Learning – Basic Level Course

My Personal Notes

Related Articles

How to read Dictionary from File in Python?