On 2014-07-06 13:09, Devin Jeanpierre wrote:
On Sun, Jul 6, 2014 at 4:51 AM,  <rxjw...@gmail.com> wrote:

I just begin to learn Python. I do not see the usefulness of '*' in its
description below:

The first metacharacter for repeating things that we'll look at is *. * doesn't
match the literal character *; instead, it specifies that the previous character
can be matched zero or more times, instead of exactly once.

For example, ca*t will match ct (0 a characters), cat (1 a), caaat (3 a
characters), and so forth.

It has to be used with other search constraints?

(BTW, this is a regexp question, not really a Python question per se.)

That's usually when it's useful, yeah. For example, [0-9] matches any
of the characters 0 through 9. So to match a natural number written in
decimal form, we might use the regexp [0-9][0-9]*, which matches the
strings "1", "12", and "007", but not "" or "Jeffrey".

Another useful one is `.*` -- `.` matches exactly one character, no
matter what that character is. So, `.*` matches any string at all.

Not quite. It won't match a '\n' unless the DOTALL flag is turned on.

The power of regexps stems from the ability to mix and match all of
the regexp pieces in pretty much any way you want.


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