How can I selectively escape percent (%) in Python strings?

Question

I have the following code

test = "have it break."
selectiveEscape = "Print percent % in sentence and not %s" % test

print(selectiveEscape)

I would like to get the output:

Print percent % in sentence and not have it break.

What actually happens:

    selectiveEscape = "Use percent % in sentence and not %s" % test
TypeError: %d format: a number is required, not str

@KarlKnechtel: But I have personally met the problem when the formatting template was read from a file. If you have no control over what is inside the file, then the question is legitimate. — pepr, May 22 '12 at 07:22
If the formatting template is in a file, then getting the template correct - including proper escaping of `%` symbols - is the responsibility of the file creator. — Karl Knechtel, May 22 '12 at 16:04
Why isn't it `\%`? That was my guess, I'm surprised to find it's `%%` instead - seems pretty counterintuitive. — Demis, Apr 28 '15 at 16:14
`% i` means "a decimal representation of an integer, padded left with spaces. — Antti Haapala, Apr 02 '16 at 21:19
The escape is to the function, not the language syntax. Hence if the escape was `\%` it would actually be `\\%` when written in ordinary code. `` is the typical pattern I've seen, and ``\`` happens to be the most common escape character, for better or worse. — shemnon, Oct 14 '16 at 21:00
@Demis and how do you escape `\ ` if you had to print `\\%`? You are bound to require escaping through repetition of special characters, if the special characters are also not special depending on circumstances. — Sassa NF, Jan 17 '17 at 21:48
I think it is annoying in Python that the the literal % is encoded by "%%" and not by "\%". — MasterControlProgram, Nov 01 '17 at 18:39
@Ralf I find it more confusing that when I need to escape `%` in LaTeX mode, `r'\%'` doesn't work but `r'\%%'` works — nish-ant, Dec 19 '19 at 16:12

score 682 · Accepted Answer · answered May 21 '12 at 00:03

682

>>> test = "have it break."
>>> selectiveEscape = "Print percent %% in sentence and not %s" % test
>>> print selectiveEscape
Print percent % in sentence and not have it break.

answered May 21 '12 at 00:03

Nolen Royalty

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In Python 3.3.5, `print('%s%%' % 100)` prints `100%`. But `print('%%')` prints `%%`. So it looks like you don't have to escape the % signs if you don't make substitutions. – Zenadix Sep 08 '15 at 19:39
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@Zenadix This is true in Python 2.7 as well – Tom Dec 15 '15 at 18:17
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Note that the `%` method is actually deprecated (in Python 3) in favor of `str.format()`: https://docs.python.org/2/library/stdtypes.html#str.format – dantiston Feb 20 '17 at 18:45
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Note that the `%` method is not depreciated in Python 3.6. It will continue to be supported in lieu of its similarity to c, c++, etc. `str.format()` and f-strings are preferred but not enforced. – Aaron Apr 07 '17 at 21:02
Just noticed that If the string is a json string, being read from a file you don't even need to escape the `%` sign. Just `%` will do – wander95 Dec 19 '17 at 16:24
You can also be sneaky and do `print "Print percent %" + "variable %s" % 'text'` as a dirty workaround. – dragon788 Dec 31 '18 at 23:35

score 60 · Answer 2 · answered May 21 '12 at 00:12

60

Alternatively, as of Python 2.6, you can use new string formatting (described in PEP 3101):

'Print percent % in sentence and not {0}'.format(test)

which is especially handy as your strings get more complicated.

answered May 21 '12 at 00:12

Karmel

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+1, while I figured op was looking for a %-based answer I much prefer to use `format` these days. – Nolen Royalty May 21 '12 at 00:18
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The only problem with this is when the text you want to format is HTML with a CSS style section. – Broseph Feb 13 '14 at 05:43
What do you recommend for text formatting HTML that contains a CSS style section, @Broseph? – DucRP Nov 10 '15 at 18:03
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I was wrong. If you use double braces in your CSS you are fine. – Broseph Jan 04 '16 at 21:36

score 43 · Answer 3 · edited May 22 '12 at 06:36

43

try using %% to print % sign .

edited May 22 '12 at 06:36

Botz3000

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answered May 21 '12 at 07:46

openmeet123

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Anthon · Answer 4 · 2016-11-28T18:43:45.667

You can't selectively escape %, as % always has a special meaning depending on the following character.

In the documentation of Python, at the bottem of the second table in that section, it states:

'%'        No argument is converted, results in a '%' character in the result.

Therefore you should use:

selectiveEscape = "Print percent %% in sentence and not %s" % (test, )

(please note the expicit change to tuple as argument to %)

Without knowing about the above, I would have done:

selectiveEscape = "Print percent %s in sentence and not %s" % ('%', test)

with the knowledge you obviously already had.

score 3 · Answer 5 · answered May 22 '12 at 07:27

If the formatting template was read from a file, and you cannot ensure the content doubles the percent sign, then you probably have to detect the percent character and decide programmatically whether it is the start of a placeholder or not. Then the parser should also recognize sequences like %d (and other letters that can be used), but also %(xxx)s etc.

Similar problem can be observed with the new formats -- the text can contain curly braces.

score 2 · Answer 6 · answered Jan 17 '20 at 11:42

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If you are using Python 3.6 or newer, you can use f-string:

>>> test = "have it break."
>>> selectiveEscape = f"Print percent % in sentence and not {test}"
>>> print(selectiveEscape)
... Print percent % in sentence and not have it break.

answered Jan 17 '20 at 11:42

Jaroslav Bezděk

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Would be nice to see how to escape { here – Sailesh Kotha Jul 08 '20 at 14:34
You just make it double `{{` – Patrik Nov 21 '20 at 16:45

How can I selectively escape percent (%) in Python strings?

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