Python dynamic function selection

[Marijan Tadin]

for rule in rules:
rule()

The following example will explain what i want to do:
rule

I expect the final function to print true, but instead i have
<function func at 0x00DC6EB0>

How do i get it to print true. I know if i had parameters in rule
like:
rule("true")
it will work. But in my case i don't need to pass any parameters.

How do i get the former method to print instead of returning a
function?

Eric

 

[Eric]

The following example will explain what i want to do: rule

I expect the final function to print true, but instead i have
<function func at 0x00DC6EB0>

How do i get it to print true. I know if i had parameters in rule
like: rule("true")
it will work. But in my case i don't need to pass any parameters.

How do i get the former method to print instead of returning a
function?

Eric

 

[Dragos Chirila]

Hi

for rule in rules:
rule()

because rule it is a function

Regards,
Dragos

----- Original Message -----
From: "Eric" <[email protected]>
Newsgroups: comp.lang.python
To: <[email protected]>
Sent: Wednesday, May 12, 2004 11:42 AM
Subject: Python dynamic function selection

 

[Tuure Laurinolli]

I expect the final function to print true, but instead i have
<function func at 0x00DC6EB0>

Why? You are not calling the function, so in the interactive interpreter
you get the representation instead.

rule("true")

Call it without passing arguments. The parentheses denote that the name
to their left is callable and should be called with whatever arguments
there are inside them, there can also be 0 arguments.

for rule in rules:
rule()

 

[Shalabh Chaturvedi]

The following example will explain what i want to do:


print "true"


rule

I expect the final function to print true, but instead i have
<function func at 0x00DC6EB0>

How do i get the former method to print instead of returning a
function?

> Eric

As others have mentioned, you have to use parenthesis () to call
anything, function or otherwise.

The function name by itself referes to the function. This feature allows
functions to be used as first-class objects easily - they can be passed
around like data.

def f():
print 'true'

g = f
g()

HTH,
Shalabh

 

[Daniel 'Dang' Griffith]

The following example will explain what i want to do:
rule

I expect the final function to print true, but instead i have
<function func at 0x00DC6EB0>

How do i get it to print true. I know if i had parameters in rule
like:
rule("true")
it will work. But in my case i don't need to pass any parameters.

How do i get the former method to print instead of returning a
function?

In Python, as in C and many other languages (but not BASIC or
Pascal/Delphi and probably others), to call/invoke/execute a function,
you need to put parentheses after the name. This is what the others'
examples have shown:
for rule in rules:
rules() # call the function
If this were not the way it worked, then in the line above it, where
you have:
rules=(func,)
it would have (called and) printed true and returned None
(implicitly), and rules would point to a (None,) tuple.

--dang