How to do regex replacement in Python using dictionary values, where the key is another matched object from the same string

Question

My regex needs to match two words in a sentence, but only the second word needs to be replaced. The first word is actually a key to a dictionary where the substitute for the second word is fetched. In PERL it would look something like:

$sentence = "Tom's boat is blue";
my %mydict = {}; # some key-pair values for name => color
$sentence =~ s/(\S+)'s boat is (\w+)/$1's boat is actually $mydict{$1}/;
print $sentence;

How can this be done in python?

Duncan · Accepted Answer · 2012-04-05 09:23:22Z

3

Something like this:

>>> sentence = "Tom's boat is blue"
>>> mydict = { 'Tom': 'green' }
>>> import re
>>> re.sub("(\S+)'s boat is (\w+)", lambda m: "{}'s boat is actually {}".format(m.group(1), mydict[m.group(1)]), sentence)
"Tom's boat is actually green"
>>>

though it would look better with the lambda extracted to a named function.

answered Apr 5, 2012 at 9:23

Duncan

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1 Comment

Benny Over a year ago

It worked perfectly, but I wonder why it is so much less intuitive than in Perl, quite contrary to my experience with Python so far.

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