Python 2 json.dump() file-like object class for tab indenting of output file.

README.md

Python 2 json.dump() file-like object class for tab indenting of output file

Using json.dump() with Python 2, indent argument is limited to number of spaces only - no ability for tabs use.

Class JSONTabIndentFileWriter provides a file-like object which will rewrite json.dump() output indending from spaces to tabs.

jsontabindentfilewriter.py

import json
import re

TEST_DICTIONARY = {
	'key1': 'value1',
	'key2': ['one','two','three','four'],
	'key3': {
		'apple': 'orange',
		'grape': 'banana',
		'tomato': ['five','six','seven','eight']
	}
}

JSON_SPACE_INDENT_COUNT = 4


class JSONTabIndentFileWriter:
	def __init__(self,filepath,indent):
		# open JSON file
		self.fh = open(filepath,'w')

		# create indent find regular expression
		self.indent_regexp = re.compile(r'^([\[,]*\r?\n)( {{{0},}})(.*)'.format(indent))
		self.indent_size = indent

	def write(self,output):
		# match JSON builder indent output
		indent_match = self.indent_regexp.search(output)

		if (indent_match):
			# swap out space indents with tabs
			output = ''.join([
				indent_match.group(1), # optional "[" or "," character before indent
				'\t' * int(len(indent_match.group(2)) / self.indent_size), # indent conversion
				indent_match.group(3) # characters past indent
			])

		# write output to file
		self.fh.write(output)

	def close(self):
		self.fh.close()

def main():
	# create JSON tab indent file writer
	json_tab_file_write = JSONTabIndentFileWriter(
		'outfile.json',
		JSON_SPACE_INDENT_COUNT
	)

	# dump TEST_DICTIONARY to JSON with tab indenting
	json.dump(
		TEST_DICTIONARY,
		json_tab_file_write,
		indent = JSON_SPACE_INDENT_COUNT,
		separators = (',',': '),
		sort_keys = True
	)

	# close file writer
	json_tab_file_write.close()


if (__name__ == '__main__'):
	main()