Steve Holden <[EMAIL PROTECTED]> wrote:
> Filip Gruszczy"ski wrote:
>> Just declaring, that they exist. Saying, that in certain function
>> there would appear only specified variables. Like in smalltalk, if I
>> remember correctly.
>>
> Icon has (had?) the same feature: if the "local" statement appeared
then
> the names listed in it could be assigned in the local namespace, and
> assignment to other names wasn't allowed.
Python being what it is, it is easy enough to add support for declaring
at the top of a function which local variables it uses. I expect that
actually using such functionality will waste more time than it saves,
but here's a simple enough implementation:
def uses(names):
def decorator(f):
used = set(f.func_code.co_varnames)
declared = set(names.split())
undeclared = used-declared
unused = declared-used
if undeclared:
raise ValueError("%s: %s assigned but not declared"
% (f.func_name, ','.join(undeclared)))
if unused:
raise ValueError("%s: %s declared but never used"
% (f.func_name, ','.join(unused)))
return f
return decorator
Used something like this:
>>> @uses("x y")
def f(x):
y = x+1
return z
>>> @uses("x y z")
def f(x):
y = x+1
return z
Traceback (most recent call last):
File "<pyshell#36>", line 1, in <module>
@uses("x y z")
File "<pyshell#32>", line 10, in decorator
raise ValueError("%s: %s declared but never used" % (f.func_name,
','.join(unused)))
ValueError: f: z declared but never used
>>> @uses("x")
def f(x):
y = x+1
return z
Traceback (most recent call last):
File "<pyshell#38>", line 1, in <module>
@uses("x")
File "<pyshell#32>", line 8, in decorator
raise ValueError("%s: %s assigned but not declared" % (f.func_name,
','.join(undeclared)))
ValueError: f: y assigned but not declared
>>>
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