List comprehension without [ ] in Python

Question

Joining a list:

>>> \'\'.join([ str(_) for _ in xrange(10) ])
\'0123456789\'

join must take an iterable.

Appa

Answer 1

>>>''.join( str(_) for _ in xrange(10) )

This is called a generator expression, and is explained in PEP 289.

The main difference between generator expressions and list comprehensions is that the former don't create the list in memory.

Note that there's a third way to write the expression:

''.join(map(str, xrange(10)))