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How to read Dictionary from File in Python?

  • Last Updated : 12 Nov, 2021

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 file in 3 ways:

  1. Using the json.loads() method : Converts the string of valid dictionary into json form.
  2. 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.
  3. 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}

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