CODEWITHSUNDEEP
python
mike
mike

Reputation: 49198

What is wrong with my attempt to do a string replace operation in Python?

What am I doing wrong here?

import re
x = "The sky is red"
r = re.compile ("red")
y = r.sub(x, "blue")
print x  # Prints "The sky is red"
print y  # Prints "blue"

How do i get it to print "The sky is blue"?

Upvotes: 2

Views: 433

Answers (5)

tzot
tzot

Reputation: 95911

By the way, for such a simple example, the re module is overkill:

x= "The sky is red"
y= x.replace("red", "blue")
print y

Upvotes: 3

Loktar
Loktar

Reputation: 546

Try:

x = r.sub("blue", x)

Upvotes: 1

Paolo Bergantino
Paolo Bergantino

Reputation: 488394

The problem with your code is that there are two sub functions in the re module. One is the general one and there's one tied to regular expression objects. Your code is not following either one:

The two methods are:

re.sub(pattern, repl, string[, count]) (docs here)

Used like so:

>>> y = re.sub(r, 'blue', x)
>>> y
'The sky is blue'

And for when you compile it before hand, as you tried, you can use:

RegexObject.sub(repl, string[, count=0]) (docs here)

Used like so:

>>> z = r.sub('blue', x)
>>> z
'The sky is blue'

Upvotes: 12

John Montgomery
John Montgomery

Reputation: 9058

You have the arguments to your call to sub the wrong way round it should be:


import re
x = "The sky is red"
r = re.compile ("red")
y = r.sub("blue", x)
print x  # Prints "The sky is red"
print y  # Prints "The sky is blue"

Upvotes: 3

Unknown
Unknown

Reputation: 46783

You read the API wrong

http://docs.python.org/library/re.html#re.sub

pattern.sub(repl, string[, count])¶

r.sub(x, "blue")
# should be
r.sub("blue", x)

Upvotes: 6

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