KeyError building parametrized string containing ':'

Question

Let's say, I need to build a series of strings based on this pattern:

pattern="{app: }"

with an ultimate goal of generating the below sequence:

"{app: MS Office }"

"{app: Notepad }" etc.

I'm trying to do that using the format method, like so

insert="MS Office"
result=pattern.format(insert)

However, all I get back is

KeyError: 'app'

It does look like the error is caused by Python misinterpreting the colon in the pattern, but what how do I get around it? I do need the colon.

Thanks.

.

Possible duplicate of [How can I print literal curly-brace characters in python string and also use .format on it?](https://stackoverflow.com/questions/5466451/how-can-i-print-literal-curly-brace-characters-in-python-string-and-also-use-fo) — awesoon, Oct 23 '18 at 17:21

score 1 · Accepted Answer · answered Oct 23 '18 at 13:10

1

You need to escape braces:

In [1]: pattern = '{{app: {}}}'

In [2]: pattern.format('MS Office')
Out[2]: '{app: MS Office}'

answered Oct 23 '18 at 13:10

awesoon

Sure, it works. Could you _explain_ the double curly braces on the outside, please? – vanhemt Oct 23 '18 at 16:28
You need to escape `{` and `}` if you want to keep them in resulting string. `format` interprets `{app}` as a place to insert value passed as `app='something'` to the function – awesoon Oct 23 '18 at 17:22
And I'm escaping them with another set of curly braces? – vanhemt Oct 23 '18 at 18:40
[Yes](https://docs.python.org/3.3/library/string.html#format-string-syntax) – awesoon Oct 23 '18 at 18:43

score 1 · Answer 2 · answered Oct 23 '18 at 13:10

1

Use

pattern="{{app: {0} }}"

insert="MS Office"
result=pattern.format(insert)
print(result)

Output:

{app: MS Office }

answered Oct 23 '18 at 13:10

Rakesh

2 Answers2