Pretty print JSON dumps
Solution 1
After years, I found a solution with the built-in pprint
module:
import pprint
d = {'a': 'blah', 'b': 'foo', 'c': [1,2,3]}
pprint.pprint(d) # default width=80 so this will be printed in a single line
pprint.pprint(d, width=20) # here it will be wrapped exactly as expected
Output:
{'a': 'blah',
'b': 'foo',
'c': [1, 2, 3]}
Solution 2
I ended up using jsbeautifier:
import jsbeautifier
opts = jsbeautifier.default_options()
opts.indent_size = 2
jsbeautifier.beautify(json.dumps(d), opts)
Output:
{
"a": "blah",
"c": [1, 2, 3],
"b": "foo"
}
Solution 3
Write your own JSON serializer:
import numpy
INDENT = 3
SPACE = " "
NEWLINE = "\n"
def to_json(o, level=0):
ret = ""
if isinstance(o, dict):
ret += "{" + NEWLINE
comma = ""
for k,v in o.iteritems():
ret += comma
comma = ",\n"
ret += SPACE * INDENT * (level+1)
ret += '"' + str(k) + '":' + SPACE
ret += to_json(v, level + 1)
ret += NEWLINE + SPACE * INDENT * level + "}"
elif isinstance(o, basestring):
ret += '"' + o + '"'
elif isinstance(o, list):
ret += "[" + ",".join([to_json(e, level+1) for e in o]) + "]"
elif isinstance(o, bool):
ret += "true" if o else "false"
elif isinstance(o, int):
ret += str(o)
elif isinstance(o, float):
ret += '%.7g' % o
elif isinstance(o, numpy.ndarray) and numpy.issubdtype(o.dtype, numpy.integer):
ret += "[" + ','.join(map(str, o.flatten().tolist())) + "]"
elif isinstance(o, numpy.ndarray) and numpy.issubdtype(o.dtype, numpy.inexact):
ret += "[" + ','.join(map(lambda x: '%.7g' % x, o.flatten().tolist())) + "]"
else:
raise TypeError("Unknown type '%s' for json serialization" % str(type(o)))
return ret
inputJson = {'a': 'blah', 'b': 'foo', 'c': [1,2,3]}
print to_json(inputJson)
Output:
{
"a": "blah",
"c": [1,2,3],
"b": "foo"
}
Solution 4
Another alternative is print(json.dumps(d, indent=None, separators=(',\n', ': ')))
The output will be:
{"a": "blah",
"c": [1,
2,
3],
"b": "foo"}
Note that though the official docs at https://docs.python.org/2.7/library/json.html#basic-usage say the default args are separators=None
--that actually means "use default of separators=(', ',': ')
). Note also that the comma separator doesn't distinguish between k/v pairs and list elements.
Basj
I work on R&D involving Python, maths, machine learning, deep learning, data science, product design, and MacGyver solutions to complex problems. I love prototyping, building proofs-of-concept. For consulting/freelancing inquiries : [email protected]
Updated on July 30, 2022Comments
-
Basj over 1 year
I use this code to pretty print a
dict
into JSON:import json d = {'a': 'blah', 'b': 'foo', 'c': [1,2,3]} print json.dumps(d, indent = 2, separators=(',', ': '))
Output:
{ "a": "blah", "c": [ 1, 2, 3 ], "b": "foo" }
This is a little bit too much (newline for each list element!).
Which syntax should I use to have this:
{ "a": "blah", "c": [1, 2, 3], "b": "foo" }
instead?