Damien Wyart wrote: > * Efrat Regev <[EMAIL PROTECTED]> in comp.lang.python: > >>Suppose I have some non-numerical Foo and would like to create a list >>of 20 Foo-s. Is there a one-step method (not a loop) of doing so? > > > Maybe : > > [ Foo ] * 20 > > or, more verbose, > > [ Foo for _ in range(20) ] >
If Foo is mutable, keep this in mind: >>> a = [ [] ]*20 # A list of 20 empty lists >>> print id(a[0]) == id(a[1]) True >>> a[0].append(1) >>> print a [[1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1], [1]] >>> >>> b = [ [] for _ in range(20) ] # A list of 20 empty lists >>> print id(b[0]) == id(b[1]) False >>> b[0].append(1) >>> print b [[1], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], [], []] -- http://mail.python.org/mailman/listinfo/python-list
