Posted by In this article, we will be doing some common operations while working with JSON data in Python
Let’s assume we have a JSON file with the following data
[
{
"color": "red",
"value": "#f00"
},
{
"color": "green",
"value": "#0f0"
},
{ ... },
{ ... },
]
I have truncated the data but it’s basically a list of objects with a color and its corresponding hex value.
Reading JSON Files
import json
path_to_file = "data.json"
with open(path_to_file) as file:
data = json.load(file)
print(data)
Pretty printing JSON
The output is hard to read, let’s improve its formatting. There are a couple of ways we can do that
import json
import pprint
path_to_file = "data.json"
with open(path_to_file) as file:
data = json.load(file)
pprint.pprint(data) # 1st Way
We can use the pretty print library.
The second way is using the JSON library the print function
import json
import pprint
path_to_file = "data.json"
with open(path_to_file) as file:
data = json.load(file)
print(json.dumps(data, indent=4, sort_keys=True)) # 2nd Way
Loading JSON from a string
We will use json.loads()
import json
import pprint
stringJSON = '''
[
{
"color": "red",
"value": "#f00"
},
{
"color": "green",
"value": "#0f0"
}
]
'''
data = json.loads(stringJSON)
pprint.pprint(data)
Converting Objects to JSON
We will use json.dumps(). Below are some commonly formated data you can convert to a JSON object.
Dictionary
import json
data = {
"key1" : "value1",
"key2" : "value2",
"key3" : "value3"
}
jsonData = json.dumps(data, indent=4)
print(jsonData)
List of Dictionaries
import json
data = [
{
"dictionary1" : "value1"
},
{
"dictionary2" : "value2"
},
{
"dictionary3" : "value3"
}
]
jsonData = json.dumps(data, indent=4)
print(jsonData)
Dictionary of Dictionaries
import json
data = {
"dictionary1" : {"key1" : "value1"},
"dictionary2" : {"key2" : "value2"},
"dictionary3" : {"key3" : "value3"}
}
jsonData = json.dumps(data, indent=4)
print(jsonData)
List of Lists
import json
data = [
[1,2,3,4],
["helo" , "world" , "python"]
]
jsonData = json.dumps(data, indent=4)
print(jsonData)
Saving JSON data into a file
We will use the json.dump() function. If the file doesn’t exist, it will create a new file. If the file does exist, it will overwrite the data in the file
import json
data = [
{
"dictionary1" : "value1"
},
{
"dictionary2" : "value2"
},
{
"dictionary3" : "value3"
}
]
nameOfFile = "jsonOutput.json"
with open(nameOfFile,"w") as file:
json.dump(data, file)
print("Saved File")
Parsing JSON
Parsing a JSON file depends on the format of the data, it could be a simple dictionary, list of dictionaries etc. The logic to parse JSON data will vary case by case. The syntax is the one we follow while traversing lists or dictionaries. The following code snippets might be helpful. In most cases, you will have to use some combination of the below cases.
Parsing JSON stored as a dictionary
This is the “Happy Case”
import json
'''
DATA FORMAT
{ "key1" : "value1",
"key2" : "value2",
"key3" : "value3"
}
'''
with open("data.json") as file:
jsonData = json.load(file)
for key,value in jsonData.items():
print(key,value)
Parsing JSON stored as a list of dictionaries
import json
'''
DATA FORMAT
[
{ "dictionary1" : "value1"},
{ "dictionary2" : "value2"},
{ "dictionary3" : "value3"}
]
'''
with open("data.json") as file:
jsonData = json.load(file)
for item in jsonData:
for key,value in item.items():
print(key,value)
Parsing JSON stored as a dictionary of dictionaries
import json
'''
DATA FORMAT
{
"dictionary1" : {"key1" : "value1"},
"dictionary2" : {"key2" : "value2"},
"dictionary3" : {"key3" : "value3"}
}
'''
with open("data.json") as file:
jsonData = json.load(file)
for jsonName,jsonObject in jsonData.items():
print(jsonName)
for key,value in jsonObject.items():
print(key,value)
Parsing JSON stored as a list of lists
import json
'''
DATA FORMAT
[
[1,2,3,4],
["helo" , "world" , "python"]
]
'''
with open("data.json") as file:
jsonData = json.load(file)
for listItem in jsonData:
for element in listItem:
print(element)
JSON Data Transformation
In the below sections we will transform some JSON Data and store it in a new file
Case1: List of Dictionaries to a Dictionary
import json
with open("data.json") as file:
jsonData = json.load(file)
result = {}
for item in jsonData:
result[item['color']] = item['value']
with open("jsonOutput.json","w") as file:
json.dump(result, file)
print("Saved File")
Case2: Dictionary of Dictionaries to a List of Dictionaries
import json
with open("data.json") as file:
jsonData = json.load(file)
result = []
for jsonName,jsonObject in jsonData.items():
result.append(jsonObject)
with open("jsonOutput.json","w") as file:
json.dump(result, file)
print("Saved File")
Case3: List of Dictionaries to a List of Lists
import json
with open("data.json") as file:
jsonData = json.load(file)
colors = []
colorValues = []
for item in jsonData:
colors.append(item['color'])
colorValues.append(item['value'])
result =[ colors , colorValues]
with open("jsonOutput.json","w") as file:
json.dump(result, file)
print("Saved File")
