Calling class method by name passed in variable

[Sagari]

Greetings,

Can someone suggest an efficient way of calling method whose name is
passed in a variable?

Given something like:

class X:
#...
def a(self):
# ...

def b(self):
# ...

#...

x = X()
#...
v = 'a'

How do I call the method of x whose name is stored in v?

PHP code for this would be:

class X {
function a() {
}
}

$x = new X();
$v = 'a';
$x->$v();

I need a solution for Python. Could you suggest anything?

The task it to call a function whose name is taken from user-supplied
input.

Thanks.

 

[Gary Herron]

Greetings,

Can someone suggest an efficient way of calling method whose name is
passed in a variable?

Given something like:

class X:
#...
def a(self):
# ...

def b(self):
# ...

#...

x = X()
#...
v = 'a'

How do I call the method of x whose name is stored in v?

Use getattr (stands for get attribute) to do this.

fn = getattr(x, v) # Get the method named by v
fn(...) # Call it

Or in one line:

getattr(x,v)(...)


Gary Herron

 

[Bruno Desthuilliers]

Sagari a écrit :

Greetings,

Can someone suggest an efficient way of calling method whose name is
passed in a variable?

method = getattr(obj, 'method_name', None)
if callable(method):
method(args)

 

[Bruno Desthuilliers]

Nick Craig-Wood a écrit :

I think that that is needless LBYL...

From experience, it isn't.

getattr(obj, 'method_name')(args)

Will produce some perfectly good exceptions

The problem is that you can't tell (without reading the exception's
message and traceback etc) if the exception happened in you code or
within the called method.

 

[Sagari]

Thanks to everyone for the advice. In fact, since all the called
methods trap necessary exceptions, I see no big problems with that.

With all respect,

Konstantin