You've tried all the variations except the one that works. The $ goes at the end of the pattern. Also, you'll want to escape the period so it actually matches a period (usually it matches any character).
r1 = re.compile(r"\.pdf$")
However, an easier and clearer way to do this is using the string's .endswith() method:
if filename.endswith(".pdf"):
# do something
That way you don't have to decipher the regular expression to understand what's going on.
Answer from kindall on Stack OverflowYou've tried all the variations except the one that works. The $ goes at the end of the pattern. Also, you'll want to escape the period so it actually matches a period (usually it matches any character).
r1 = re.compile(r"\.pdf$")
However, an easier and clearer way to do this is using the string's .endswith() method:
if filename.endswith(".pdf"):
# do something
That way you don't have to decipher the regular expression to understand what's going on.
Behaviour of re.match() and re.search()
There is one significant difference: re.match() checks the beginning of string, you are most likely looking for re.search().
Comparison of both methods is clearly shown in the Python documentation chapter called "search() vs. match()"
Special characters in regular expression
Also the meaning of characters in regular expressions is different than you are trying to use it (see Regular Expression Syntax for details):
^matches the beginning:(Caret.) Matches the start of the string, and in MULTILINE mode also matches immediately after each newline.
$matches the end:Matches the end of the string or just before the newline at the end of the string, and in
MULTILINEmode also matches before a newline. foo matches both ‘foo’ and ‘foobar’, while the regular expressionfoo$matches only ‘foo’. More interestingly, searching for foo.$ in 'foo1\nfoo2\n' matches ‘foo2’ normally, but ‘foo1’ inMULTILINEmode; searching for a single$in 'foo\n' will find two (empty) matches: one just before the newline, and one at the end of the string.
Complete answer
The solution you are looking for may be:
import re
r1 = re.compile("\.pdf$") # regular expression corrected
if r1.search("spam.pdf"): # re.match() replaced with re.search()
print "yes"
else:
print "no"
which checks, if the string ends with ".pdf". Does the same as kindall's answer with .endswith(), but if kindall's answer works for you, choose it (it is cleaner as you may not need regular expressions at all).
The problem is that your pattern matches any string that comes after by test_ and before .py, but that doesn't restrict it from having other characters before the test_ or after the .py.
You need to use start (^) and end ($) anchors. Also, don't forget to escape the . character. Try this pattern:
(?<=^test_).+(?=\.py$)
Look at this:
import re
files = [
"test_1.py",
"Test.py",
"test.pyc",
"test.py",
"script.py"]
print [x for x in files if re.search("^test_.*py$", x)]
output:
['test_1.py']
(^A.*B$)|(^A.*$)|(^.*B$)
Is this the desired behavior?
var rx = /^((?:A)?)(.*?)((?:B)?)$/;
"Aanything".match(rx)
> ["Aanything", "A", "anything", ""]
"anythingB".match(rx)
> ["anythingB", "", "anything", "B"]
"AanythingB".match(rx)
> ["AanythingB", "A", "anything", "B"]
"anything".match(rx)
> ["anything", "", "anything", ""]
"AanythingB".replace(rx, '$1nothing$3');
> "AnothingB"
"AanythingB".replace(rx, '$2');
> "anything"