Python json dump

Question

I have a JSON file that looks like this:

{"environment": "production", 
 "classes": 
    {"nfs::server": {"exports": ["/srv/share1","/srv/share3"]}}
}

When I run the following code using Python 3.6

fp=open('example.json', 'r')
data=json.load(fp)

print(50*'-')
print(json.dumps(data, indent=4))
print(50*'-')
json.dump(data, sys.stdout, indent=4)

I get the output:

--------------------------------------------------
{
    "environment": "production",
    "classes": {
        "nfs::server": {
            "exports": [
                "/srv/share1",
                "/srv/share3"
            ]
        }
    }
}
--------------------------------------------------
{
    "environment": "production",
    "classes": {
        "nfs::server": {
            "exports": [
                "/srv/share1",
                "/srv/share3"
            ]
        }
    }
}%

My question is why is the extra % included in the json.dump output compared to the json.dumps string? It is not an artifact of the OS because if I provide a file object instead of sys.stdout it also gets written to the file.

Could this be an artifact of an encoding mismatch?

Todd Holmberg
– Todd Holmberg

2017-03-24 14:36:48 +00:00
Commented Mar 24, 2017 at 14:36 — Todd Holmberg
– Todd Holmberg, Commented Mar 24, 2017 at 14:36
Issue observable only using zsh, not using bash

Paul Joireman
– Paul Joireman

2017-03-24 14:59:53 +00:00
Commented Mar 24, 2017 at 14:59 — Paul Joireman
– Paul Joireman, Commented Mar 24, 2017 at 14:59

Community · Accepted Answer · 2017-04-13 12:36:31Z

5

The last % is the first character of your console prompt line or a feature of your shell (https://unix.stackexchange.com/questions/167582/why-zsh-ends-a-line-with-a-highlighted-percent-symbol)

Nothing to do with json, nor python.

Because, when print() add a '\n' at the end, the dump to stdout doesn't

edited Apr 13, 2017 at 12:36

CommunityBot

11 silver badge

answered Mar 24, 2017 at 14:33

yota

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8 Comments

yota Over a year ago

it does not :) sys.stdout is not a file, it's the standard output (ie. console). What the OP copy-pasted may be what was displayed in his console... hence the spurious % char

yota Over a year ago

because, if the OP does a cat file.txt, the result is the same, with not trailing \n, he see the next % of the prompt :) (just a guess)

yota Over a year ago

you are right, me neither, but when I forget the trailing \n I still get a %: echo -n tutu tutu%... It may still be due to the shell behavior and not python

Paul Joireman Over a year ago

I think it is a shell thing. Although I have no % in my shell prompt (using zsh), if I switch to bash this problem disappears. Thanks for the help guys.

Todd Holmberg Over a year ago

I just had the same thing happen using zsh. Adding a newline fixed it. Good to know.

|

Apalala · Accepted Answer · 2017-03-24 14:35:42Z

4

The reason is that print(json.dumps(data, indent=4)) prints a newline, and json.dump(data, sys.stdout, indent=4) does not.

You can try adding a print() at the end:

print(50*'-')
print(json.dumps(data, indent=4))
print(50*'-')
json.dump(data, sys.stdout, indent=4)
print()

Is the % symbol part of your shell's prompt?

answered Mar 24, 2017 at 14:35

Apalala

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2 Comments

Paul Joireman Over a year ago

While this solves the problem of output to the console, it does not solve output to a file, ie. replace sys.stdout with a file object. My shell prompt has no % but it is still output to a file when using json.dump

Paul Joireman Over a year ago

It's ultimately a shell issue, using zsh I observe the trailing % but with bash no trailing %. Thanks for the help guys.

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