Escape single '{' in python

Question

I am using python for C code generation, I want to have a function that prints the following:

{
.data1="egg",
.data2="dog",
},

I tried this function:

def funky(data1,data2):
    return """\
    {
    .data1="egg",
    .data2="dog",
    },""".format(data1,data2)

Calling "funky("egg","dog")" results in a KeyError. Relating to the unpaired curly braces.

How can I print these braces?

Why are you using `format` at all when your format string is completely hardcoded, with no format placeholders? — user2357112, Mar 20 '18 at 17:42
Seems to me, like this question has already been answered [here](https://stackoverflow.com/questions/5466451/how-can-i-print-literal-curly-brace-characters-in-python-string-and-also-use-fo). — G.Brown, Mar 20 '18 at 17:44

score 3 · Accepted Answer · answered Mar 20 '18 at 17:51

3

You would need to:

Use two {s and two }s.
Escape the double quotes inside the string.
Use {0} and {1} instead of {egg} and {dog}.

def funky(data1,data2):
    return """\
    {{
    .data1=\"{0}\",
    .data2=\"{1}\",
    }},""".format(data1,data2)

answered Mar 20 '18 at 17:51

R Sahu

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Andrey Tyukin · Answer 2 · 2018-03-20T18:34:50.713

You have no variables in your string literal, you didn't escape the { and }, and you broke the indentation. Try this:

def stripMargin(txt):
  return '\n'.join([r.split('|', 1)[1] for r in txt.split('\n')])

def funky(data1,data2):
  return stripMargin("""|{{
  |.data1="{0}",
  |.data2="{1}",
  |}},""".format(data1,data2))

print(funky("egg", "dog"))

The |-part combined with stripMargin ensures that the indentation of the generated code (the object language) does not interfere with the indentation of python (the metalanguage).

I would actually indent the generated code differently:

def funky(data1,data2):
  return stripMargin("""|{{
  |  .data1="{0}",
  |  .data2="{1}",
  |}},""".format(data1,data2))

Since you don't need any common indentation in the final output, you can also use dedent:

from textwrap import dedent

def funky2(data1,data2):
    return dedent("""\
    {{
    .data1="{0}",
    .data2="{1}",
    }},""").format(data1,data2)

(Thanks @user2357112 for pointing it out)

The closest thing to Scala's `stripMargin` in Python is [`textwrap.dedent`](https://docs.python.org/3/library/textwrap.html#textwrap.dedent). — user2357112, Mar 20 '18 at 18:22
@user2357112 Thanks for the hint! Added a variation with `dedent`. — Andrey Tyukin, Mar 20 '18 at 18:35

Escape single '{' in python

2 Answers2