data is a Python dictionary. It needs to be encoded as JSON before writing.

Use this for maximum compatibility (Python 2 and 3):

import json
with open('data.json', 'w') as f:
    json.dump(data, f)

On a modern system (i.e. Python 3 and UTF-8 support), you can write a nicer file using:

import json
with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False, indent=4)

See json documentation.

Use the ensure_ascii=False switch to json.dumps(), then encode the value to UTF-8 manually:

>>> json_string = json.dumps("ברי צקלה", ensure_ascii=False).encode('utf8')
>>> json_string
b'"\xd7\x91\xd7\xa8\xd7\x99 \xd7\xa6\xd7\xa7\xd7\x9c\xd7\x94"'
>>> print(json_string.decode())
"ברי צקלה"

If you are writing to a file, just use json.dump() and leave it to the file object to encode:

with open('filename', 'w', encoding='utf8') as json_file:
    json.dump("ברי צקלה", json_file, ensure_ascii=False)

Caveats for Python 2

For Python 2, there are some more caveats to take into account. If you are writing this to a file, you can use io.open() instead of open() to produce a file object that encodes Unicode values for you as you write, then use json.dump() instead to write to that file:

with io.open('filename', 'w', encoding='utf8') as json_file:
    json.dump(u"ברי צקלה", json_file, ensure_ascii=False)

Do note that there is a bug in the json module where the ensure_ascii=False flag can produce a mix of unicode and str objects. The workaround for Python 2 then is:

with io.open('filename', 'w', encoding='utf8') as json_file:
    data = json.dumps(u"ברי צקלה", ensure_ascii=False)
    # unicode(data) auto-decodes data to unicode if str
    json_file.write(unicode(data))

In Python 2, when using byte strings (type str), encoded to UTF-8, make sure to also set the encoding keyword:

>>> d={ 1: "ברי צקלה", 2: u"ברי צקלה" }
>>> d
{1: '\xd7\x91\xd7\xa8\xd7\x99 \xd7\xa6\xd7\xa7\xd7\x9c\xd7\x94', 2: u'\u05d1\u05e8\u05d9 \u05e6\u05e7\u05dc\u05d4'}

>>> s=json.dumps(d, ensure_ascii=False, encoding='utf8')
>>> s
u'{"1": "\u05d1\u05e8\u05d9 \u05e6\u05e7\u05dc\u05d4", "2": "\u05d1\u05e8\u05d9 \u05e6\u05e7\u05dc\u05d4"}'
>>> json.loads(s)['1']
u'\u05d1\u05e8\u05d9 \u05e6\u05e7\u05dc\u05d4'
>>> json.loads(s)['2']
u'\u05d1\u05e8\u05d9 \u05e6\u05e7\u05dc\u05d4'
>>> print json.loads(s)['1']
ברי צקלה
>>> print json.loads(s)['2']
ברי צקלה

You don't dump a string but to a string.

d = {"foo": "bar"}
j = json.dumps(d)
print(j)

Output:

{"foo": "bar"}

It makes no sense to use a string as the argument of json.dumps which is expecting a dictionary or a list/tuple as the argument.

Serialize obj to a JSON formatted str using this conversion table.