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?
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"
}
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"
}
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.
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]}
I couldn't get jsbeautifier to do much, so I used regular expressions. Had json pattern like
'{\n "string": [\n 4,\n 1.0,\n 6,\n 1.0,\n 8,\n 1.0,\n 9,\n 1.0\n ],\n...'
that I wanted as
'{\n "string": [ 4, 1.0, 6, 1.0, 8, 1.0, 9, 1.0],\n'
so
t = json.dumps(apriori, indent=4)
t = re.sub('\[\n {7}', '[', t)
t = re.sub('(?<!\]),\n {7}', ',', t)
t = re.sub('\n {4}\]', ']', t)
outfile.write(t)
So instead of one "dump(apriori, t, indent=4)", I had those 5 lines.
This has been bugging me for a while as well, I found a 1 liner I'm almost happy with:
print json.dumps(eval(str(d).replace('[', '"[').replace(']', ']"').replace('(', '"(').replace(')', ')"')), indent=2).replace('\"\\"[', '[').replace(']\\"\"', ']').replace('\"\\"(', '(').replace(')\\"\"', ')')
That essentially convert all lists or tuples to a string, then uses json.dumps with indent to format the dict. Then you just need to remove the quotes and your done!
Note: I convert the dict to string to easily convert all lists/tuples no matter how nested the dict is.
PS. I hope the Python Police won't come after me for using eval... (use with care)
Perhaps not quite as efficient, but consider a simpler case (somewhat tested in Python 3, but probably would work in Python 2 also):
def dictJSONdumps( obj, levels, indentlevels = 0 ):
import json
if isinstance( obj, dict ):
res = []
for ix in sorted( obj, key=lambda x: str( x )):
temp = ' ' * indentlevels + json.dumps( ix, ensure_ascii=False ) + ': '
if levels:
temp += dictJSONdumps( obj[ ix ], levels-1, indentlevels+1 )
else:
temp += json.dumps( obj[ ix ], ensure_ascii=False )
res.append( temp )
return '{\n' + ',\n'.join( res ) + '\n}'
else:
return json.dumps( obj, ensure_ascii=False )
This might give you some ideas, short of writing your own serializer completely. I used my own favorite indent technique, and hard-coded ensure_ascii, but you could add parameters and pass them along, or hard-code your own, etc.
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