Re: block/lambda

[Jean-Paul Calderone]

On Tue, 29 Jul 2008 07:26:38 -0700 (PDT), "ji***********@gmail.com" <ji***********@gmail.comwrote:

>

>2. Will it be possible in Python 3.0 to do the following:

>>def dotimes(n, callable):

for i in range(n): callable()

>>def block():

nonlocal i
for j in range(i):
print j,
print

dotimes seems ok and what is wrong with that function "block"? You do
not need to specify that i is "nonlocal", global i will be used.

>>>i=10
def block():

for j in range(i):
print j,
print

>>>block()

0 1 2 3 4 5 6 7 8 9

Python doesn't have dynamic scoping.

>>def dotimes(n, callable):

... for i in range(n):
... callable()
...

>>def block():

... for j in range(i):
... print j,
... print
...

>>def f():

... dotimes(5, block)
...

>>f()

Traceback (most recent call last):
File "<stdin>", line 1, in ?
File "<stdin>", line 2, in f
File "<stdin>", line 3, in dotimes
File "<stdin>", line 2, in block
NameError: global name 'i' is not defined

>>>

The "nonlocal" keyword in Python 3 won't do this, either. It's for
referencing names in outer lexical scopes, not outer dynamic scopes.

Jean-Paul