I am trying to interpolate this string correctly:
/test/test?Monetization%20Source=%d&Channel%20Id=%d' % (mid, cid)
I want the the %20 to rendered as is and the %d to serve as place-holderes for the variables mid and cid. How do I do this?
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4 Answers
In general, you want urllib.urlencode:
import urllib
url = '/test/test?' + urllib.urlencode({
'Monetization Source': mid,
'Channel Id': cid,
})
Comments
I presume this is a constant string literal? If so it's easy - just double up the percent signs you want to keep.
'/test/test?Monetization%%20Source=%d&Channel%%20Id=%d' % (mid, cid)
3 Comments
Karl Knechtel
This is the correct answer to the question, but not the correct solution for the problem.
Mark Ransom
@Karl, unless you can point to a case that makes this fail, it's no less "correct" than any other answer. I don't disagree that there might be a better approach, and I've already given my +1.
Karl Knechtel
Correctness in solutions is also about maintainability, clarity and expressiveness.
Since Python 2.6, you can use the Format Specification Mini-Language, which is way more powerful than the old (but still supported) % operator.
>>> mid=4
>>> cid=6
>>> "/test/test?Monetization%20Source={0:d}&Channel%20Id={1:d}".format(mid, cid)
'/test/test?Monetization%20Source=4&Channel%20Id=6'
Omitting the :d for integers defaults to str()
Since Python 2.7 and 3.2, you can omit the parameter indexes:
>>> "...ce={:d}&Channel%20Id={:d}"...
But see the manual, the format() methods and built-in function are very flexible and useful.
1 Comment
Mark Ransom
Hopefully then the string doesn't have any
{ in it, or I see another question coming...With 'f-string'(introduced in Python 3.6), it's eaiser to achieve interpolation.
f-string or formatted-string provides a way of formatting strings using a minimal syntax.‘f’ or ‘F’ is used as a prefix and curly braces { } are used as placeholders.
mid=1.1
cid=1.2
print(f"Default:\n /test/test?Monetization%20Source={mid}&Channel%20Id={cid}")
your output will be,
Default:
/test/test?Monetization%20Source=1.1&Channel%20Id=1.2
if the string literal has curly braces { } as a part of a string itself, then you have to double the braces to let interpreter know that braces are part of the string literal and not a place holder.
print(f"With curly braces:\n /test/test?{{Monetization}}%20Source={mid}&Channel%20Id={cid}")
here, {Monetization} is a part of the string literal itself and hence additional curly braces are used as {{Monetization}}
output is,
With curly braces:
/test/test?{Monetization}%20Source=1.1&Channel%20Id=1.2
