json.dump() in Python

The full-form of JSON is JavaScript Object Notation. It means that a script (executable) file which is made of text in a programming language, is used to store and transfer the data. Python supports JSON through a built-in package called

json

. To use this feature, we import the json package in Python script. The text in JSON is done through quoted-string which contains the value in key-value mapping within

{ }

. It is similar to the dictionary in Python.

json.dump()

json

module in Python module provides a method called

dump()

which converts the Python objects into appropriate json objects. It is a slight variant of

dumps()

method.

Difference between dump() and dumps()

dump() and its arguments

Syntax: json.dump(d, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None)

Parameters:

• indent : It improves the readability of the json file. The possible values that can be passed to this parameter are simply double quotes(""), any integer values. Simple double quotes makes every key-value pair appear in new line. Example: Python3 1==

  import json
  
  # python object(dictionary) to be dumped
  dict1 ={
      "emp1": {
          "name": "Lisa",
          "designation": "programmer",
          "age": "34",
          "salary": "54000"
      },
      "emp2": {
          "name": "Elis",
          "designation": "Trainee",
          "age": "24",
          "salary": "40000"
      },
  }
  
  # the json file where the output must be stored
  out_file = open("myfile.json", "w")
  
  json.dump(dict1, out_file, indent = 6)
  
  out_file.close()
  

  Output:
• skipkeys: If the key is not of standard allowed types like int, float, string, None or bool, error will be generated while dumping them. To avoid that if this parameter is set to true. Example: Python

  import json
   
  # python object(dictionary) to be dumped
  dict1 ={
      ('addresss', 'street'):'Brigade road',
  }
   
  # the json file where the output must be stored
  out_file = open("myfile.json", "w")
   
  json.dump(dict1, out_file, indent = 6)
   
  out_file.close()
  

  Output: If skipkeys is not set to true, then the following error will be generated :
• separator: This parameter takes up either one or two values. The first value specifies the symbol that separates one key-value pair from another. The next one specifies the symbol that separates the value from its key.
• sort_keys: This parameter takes Boolean value. If it is set to True, the keys are set in ascending order else, they appear as in the Python object
• ensure_ascii: This parameter also takes only Boolean values. If it is not set to true the non-ASCII characters are dumped into the output file as it is. By default the value is true. See the two codes below to get the difference. Example 1: Python3 1==

  # dictionary to be dumped
  d ={'lang':'??? ????'}
  
  with open('myfile.json', 'w', encoding ='utf8') as json_file:
      json.dump(d, json_file, ensure_ascii = False)
  

  Output:Example 2: If it is set to True, then the content of the json file will be: Python

  import json
  
  
  # dictionary to be dumped
  d ={'lang':'??? ????'}
  
  with open('myfile.json', 'w', encoding ='utf8') as json_file:
      json.dump(d, json_file, ensure_ascii = True)
  

  Output:
• allow_nan: It helps to serialize the range of float values. Example 1: Python

  import json
  
  
  # dictionary to be dumped
  d ={
      'a':1,
      'x':float('nan')
  }
  
  with open('myfile.json', 'w', encoding ='utf8') as json_file:
      json.dump(d, json_file, allow_nan=False)
  

  Output:Example 2: If it is set to True, the error will not be generated. The content in the json file will be : Python

  import json
  
  
  # dictionary to be dumped
  d ={
      'a':1,
      'x':float('nan')
  }
  
  with open('myfile.json', 'w', encoding ='utf8') as json_file:
      json.dump(d, json_file, allow_nan=True)
  

  Output:
  

• json.dump(): This function serializes a Python object (like a dict) to a JSON formatted file object. It directly writes JSON-encoded data to a file-like object (e.g., a file opened with open() in write mode).
• json.dumps(): This function serializes a Python object (like a dict) to a JSON formatted string. It returns a JSON string representation of the Python object.