Let’s start the year with a small piece of code that I could not figure out right off the bat.

It is a side piece of my Web-Scraping series, as manipulating JSONs is a big part of that.

Now with code highlighting!

The problem here is that in order to succesfull json.load(file) this file needs to content at least two brackets {}. The easiest way is to create such file before trying to populate it with data.

file_path = 'my.json'
if not os.path.isfile(file_path):
	with open(file_path , 'w+', encoding='utf-8') as f:
		f.write('{"something": 0}')
		f.close()

Basically I check if a file does not exists and open it with w+. I don’t want it to be rewritten if it already exists and contain data I wrote. If there is a finer solution, please share. This whole task tortured me enough to seek it myself.

Don’t forget to use encoding=’utf-8′ if you have any letters but a-Az-Z.

I populated the file with {"something": 0} in case you want to use jsondata.update() – it requires for both dicts to be no empty.

And then open this file with r+ and update it.

with open(PATH, 'r+', encoding='utf-8') as jsonFile:
	data = json.load(jsonFile)

	jsonFile.seek(0)
	jsonFile.truncate()


        # updating
	data.update(to_add)


	json.dump(data, jsonFile, ensure_ascii=False)
	jsonFile.close()

In order to properly rewrite the file, after you read it, you need to jump back to the 0 symbol and cut everything off.

As I have already said, you can do two things. If you just want to add keys with their respective values, use data.update(). If not and you want to, say, update a list value of a key, it won’t happen – data.update() will just replace the old list with the new list. So iterate your keys and update the old dictionary the good old way.