Albert Hopkins <mar...@letterboxes.org> wrote: > On Fri, 2009-03-13 at 21:01 +0000, tinn...@isbd.co.uk wrote: > > I've had this trouble before, how do I find the details of how "in" > > works in the documentation. E.g. the details of:- > > > > if string in bigstring: > > > > It gets a mention in the "if" section but not a lot. > > > > >From http://docs.python.org/reference/expressions.html#in > > The operators in and not in test for collection membership. x in > s evaluates to true if x is a member of the collection s, and > false otherwise. x not in s returns the negation of x in s. The > collection membership test has traditionally been bound to > sequences; an object is a member of a collection if the > collection is a sequence and contains an element equal to that > object. However, it make sense for many other object types to > support membership tests without being a sequence. In > particular, dictionaries (for keys) and sets support membership > testing. > > For the list and tuple types, x in y is true if and only if > there exists an index i such that x == y[i] is true. > > For the Unicode and string types, x in y is true if and only if > x is a substring of y. An equivalent test is y.find(x) != -1. > Note, x and y need not be the same type; consequently, u'ab' in > 'abc' will return True. Empty strings are always considered to > be a substring of any other string, so "" in "abc" will return > True. > > Changed in version 2.3: Previously, x was required to be a > string of length 1. > > For user-defined classes which define the __contains__() method, > x in y is true if and only if y.__contains__(x) is true. > > For user-defined classes which do not define __contains__() and > do define __getitem__(), x in y is true if and only if there is > a non-negative integer index i such that x == y[i], and all > lower integer indices do not raise IndexError exception. (If any > other exception is raised, it is as if in raised that > exception). > That's what I wanted, thanks, I maybe didn't stare hard enough at the expressions section.
-- Chris Green -- http://mail.python.org/mailman/listinfo/python-list
