RanRag has already answered it for your specific question.

However, more generally, what you are doing with

if [[ "$string" =~ ^hello ]]

is a regex match. To do the same in Python, you would do:

import re
if re.match(r'^hello', somestring):
    # do stuff

Obviously, in this case, somestring.startswith('hello') is better.

re.match will match the string at the beginning, in contrast to re.search:

re.match(r'(ftp|http)://.*\.(jpg|png)$', s)

Two things to note here:

• r'' is used for the string literal to make it trivial to have backslashes inside the regex
• string is a standard module, so I chose s as a variable
• If you use a regex more than once, you can use r = re.compile(...) to built the state machine once and then use r.match(s) afterwards to match the strings

If you want, you can also use the urlparse module to parse the URL for you (though you still need to extract the extension):

>>> allowed_schemes = ('http', 'ftp')
>>> allowed_exts = ('png', 'jpg')
>>> from urlparse import urlparse
>>> url = urlparse("ftp://www.somewhere.com/over/the/rainbow/image.jpg")
>>> url.scheme in allowed_schemes
True
>>> url.path.rsplit('.', 1)[1] in allowed_exts
True