JSON: Difference between json.dump() and json.dumps()

In a nutshell:

• The json.dumps()method can convert a Python object into a JSON string.

• The json.dump()method can be used for writing/dumping JSON to a file/socket.

There are also minor differences on the ensure_ascii behavior. This difference is related to how the underlying write() function works. It operates in chunks rather than working on the whole string:

• json.dump()

  Serializes obj as a JSON-formatted stream to fp (a .write()-supporting file-like object). If ensure_ascii is false, some chunks written to fp may be unicode instances.

• json.dumps()

  Serializes obj to a JSON formatted str. If ensure_ascii is false, the result may contain non-ASCII characters and the return value may be a unicode instance.

The following sections provide more details.

json.dumps()

According to the Python documentation:

• Syntax: json.dumps(dict, indent)

• Parameters:

  • Dictionary: Name of the dictionary that should be converted to a JSON object
  • Indent: Defines the number of units for indentation

# Python program to convert 
# Python to JSON 

import json 

# Data to be written 
dictionary ={ 
"testId": "12", 
"name": "LoadPage", 
"Group": "Regressions"} 

# Serializing json 
json_object = json.dumps(dictionary, indent = 4) 
print(json_object) 

{
    "group": "Regressions",
    "name": "LoadPage",
    "testId": "12"   
}

json.dump()

According to the Python documentation:

• Syntax: json.dump(dict, file_pointer)

• Parameters:

  • Dictionary: Name of the dictionary that should be converted to a JSON object
  • File pointer: Pointer of the file opened in write or append mode

# Python program to write JSON 
# to a file 


import json 

# Data to be written 
dictionary ={ 
    "testName" : "page load", 
    "steps" : 56, 
    "timeout" : 8.6, 
    "Suit" : "Smoke Test v.2865"} 

with open("sample.json", "w") as outfile: 
    json.dump(dictionary, outfile) 

{"testname": "page load", "steps": 56, "timeout": 8.6, "Suit": "Smoke Test v.2865"}