assignment in if

[Gary Wessle]

Hi

is there a way to make an assignment in the condition of "if" and use
it later, e.g.

nx = re.compile('reg ex')
if nx.search(text) :
funCall(text, nx.search(text) )

nx.search(text) is evaluated twice, I was hoping for something like

nx = re.compile('reg ex')
if x = nx.search(text) :
funCall(text, x))

thanks

[Roy Smith]

Re: assignment in if

In article <87iroodnqz.fsf @localhost.loca ldomain>,
Gary Wessle <phddas@yahoo.c om> wrote:
[color=blue]
> Hi
>
> is there a way to make an assignment in the condition of "if" and use
> it later, e.g.
>
> nx = re.compile('reg ex')
> if nx.search(text) :
> funCall(text, nx.search(text) )
>
> nx.search(text) is evaluated twice, I was hoping for something like
>
> nx = re.compile('reg ex')
> if x = nx.search(text) :
> funCall(text, x))[/color]

Personally, I find the C-style idiom you long for to be convenient and
useful. That being said, it does not exist in Python, by deliberate design
decision. In Python, assignment is not an operator with side effects like
in C or Java, but a statement. What you need to do is:

nx = re.compile('reg ex')
x = nx.search(text)
if x:
funCall(text, x))

The lack of embedded assignments leads to slightly more verbose code in
situations like this, but on the other hand, it avoids the typical C
disaster of writing a whole function as a one liner.

[Bruno Desthuilliers]

Re: assignment in if

Gary Wessle a écrit :[color=blue]
> Hi
>
> is there a way to make an assignment in the condition of "if" and use
> it later[/color]

No.
[color=blue]
>, e.g.
>
> nx = re.compile('reg ex')
> if nx.search(text) :
> funCall(text, nx.search(text) )
>
> nx.search(text) is evaluated twice, I was hoping for something like
>
> nx = re.compile('reg ex')
> if x = nx.search(text) :
> funCall(text, x))[/color]

x = nx.search(text)
if x:
funCall(text, x)

[Ben Caradoc-Davies]

Re: assignment in if

Gary Wessle wrote:[color=blue]
> is there a way to make an assignment in the condition of "if"[/color]

No.
[color=blue]
> nx = re.compile('reg ex')
> if x = nx.search(text) :
> funCall(text, x))[/color]

Use:

nx = re.compile('reg ex')
x = nx.search(text)
if x:
funCall(text, x)

--
Ben Caradoc-Davies <ben@wintersun. org>

http://wintersun.org/

"Those who deny freedom to others deserve it not for themselves."
- Abraham Lincoln

[Edward Elliott]

Re: assignment in if

Roy Smith wrote:[color=blue]
> decision. In Python, assignment is not an operator with side effects like
> in C or Java, but a statement.[/color]

<nitpick> assignemnt is actually an expression in those languages, not a
statement. </nitpick>
[color=blue]
> The lack of embedded assignments leads to slightly more verbose code in
> situations like this, but on the other hand, it avoids the typical C
> disaster of writing a whole function as a one liner.[/color]

Writing disasters in python just takes a little more creativity. ;)

[Bruno Desthuilliers]

Re: assignment in if

Edward Elliott a écrit :[color=blue]
> Roy Smith wrote:
>[/color]
(snip)
[color=blue][color=green]
>>The lack of embedded assignments leads to slightly more verbose code in
>>situations like this, but on the other hand, it avoids the typical C
>>disaster of writing a whole function as a one liner.[/color]
>
> Writing disasters in python just takes a little more creativity. ;)
>[/color]
+1 QOTW

[Edward Elliott]

Re: assignment in if

Edward Elliott wrote:[color=blue]
> <nitpick> assignemnt is actually an expression in those languages, not a
> statement. </nitpick>[/color]

s/statement/operator/

[Edward Elliott]

Re: assignment in if

Edward Elliott wrote:[color=blue]
> Edward Elliott wrote:[color=green]
>> <nitpick> assignemnt is actually an expression in those languages, not a
>> statement. </nitpick>[/color]
>
> s/statement/operator/[/color]

<shakes head>
it was probably clearer the first time, but let me rephrase:
in C/Java, assignment is neither a statement not an operator. it is an
expression involving a certain operator. that operator (not so)
coincidentally happens to be the assignment operator, or one of its
variants.

ah forget it, replying to your reply to yourself is probably illegal...