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Why Python allows comparison of a callable and a number?

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newptcai at gmail

Nov 22, 2009, 4:03 AM

Post #1 of 3 (186 views)
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Why Python allows comparison of a callable and a number?

I used python to write an assignment last week, here is a code snippet

#================================

def departTime():
'''
Calculate the time to depart a packet.
'''
if(random.random < 0.8):
t = random.expovariate(1.0 / 2.5)
else:
t = random.expovariate(1.0 / 10.5)
return t

#================================

Can you see the problem? I compare random.random with 0.8, which
should be random.random().

Of course this because of my careless, but I don't get it. In my
opinion, this kind of comparison should invoke a least a warning in
any programming language.

So why does python just ignore it?
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clp2 at rebertia

Nov 22, 2009, 4:09 AM

Post #2 of 3 (184 views)
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Re: Why Python allows comparison of a callable and a number? [In reply to]

On Sun, Nov 22, 2009 at 4:03 AM, 一首诗 <newptcai [at] gmail> wrote:
> I used python to write an assignment last week, here is a code snippet
>
> #================================
>
> def departTime():
> '''
> Calculate the time to depart a packet.
> '''
> if(random.random < 0.8):
> t = random.expovariate(1.0 / 2.5)
> else:
> t = random.expovariate(1.0 / 10.5)
> return t
>
> #================================
>
> Can you see the problem? I compare random.random with 0.8, which
> should be random.random().
>
> Of course this because of my careless, but I don't get it. In my
> opinion, this kind of comparison should invoke a least a warning in
> any programming language.
>
> So why does python just ignore it?

It's an historical anomaly that's been rectified in Python 3, where
such non-equality comparisons between unrelated types *do* now raise
an error.

Cheers,
Chris
--
http://blog.rebertia.com
--
http://mail.python.org/mailman/listinfo/python-list

python at mrabarnett

Nov 22, 2009, 8:23 AM

Post #3 of 3 (174 views)
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Re: Why Python allows comparison of a callable and a number? [In reply to]

一首诗 wrote:
> I used python to write an assignment last week, here is a code snippet
>
> #================================
>
> def departTime():
> '''
> Calculate the time to depart a packet.
> '''
> if(random.random < 0.8):
> t = random.expovariate(1.0 / 2.5)
> else:
> t = random.expovariate(1.0 / 10.5)
> return t
>
> #================================
>
> Can you see the problem? I compare random.random with 0.8, which
> should be random.random().
>
> Of course this because of my careless, but I don't get it. In my
> opinion, this kind of comparison should invoke a least a warning in
> any programming language.
>
> So why does python just ignore it?

In Python 2 you can compare any 2 objects, for example an int with a
string. The result is arbitrary but consistent.

In Python 3 if the 2 objects aren't 'compatible' you'll get a TypeError
at runtime.

BTW, you don't need to put parentheses around the conditions in 'if' and
'while' statements. Python isn't C, etc. :-)
--
http://mail.python.org/mailman/listinfo/python-list

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