Call a Python method by name [duplicate]
If I have an object and a method name in a string, how can I call the method?
class Foo:
def bar1(self):
print 1
def bar2(self):
print 2
def callMethod(o, name):
???
f = Foo()
callMethod(f, "bar1")
Use the built-in getattr()
function:
class Foo:
def bar1(self):
print(1)
def bar2(self):
print(2)
def call_method(o, name):
return getattr(o, name)()
f = Foo()
call_method(f, "bar1") # prints 1
You can also use setattr()
for setting class attributes by names.
I had similar question, wanted to call instance method by reference. Here are funny things I found:
instance_of_foo=Foo()
method_ref=getattr(Foo, 'bar')
method_ref(instance_of_foo) # instance_of_foo becomes self
instance_method_ref=getattr(instance_of_foo, 'bar')
instance_method_ref() # instance_of_foo already bound into reference
Python is amazing!
getattr(globals()['Foo'](), 'bar1')()
getattr(globals()['Foo'](), 'bar2')()
No need to instantiate Foo first!
def callmethod(cls, mtd_name):
method = getattr(cls, mtd_name)
method()
Here is a more generalized version using Python decorators. You can call by short or long name. I found it useful when implementing CLI with short and long sub commands.
Python decorators are wonderful. Bruce Eckel (Thinking in Java) describes Python decorators beautifully here.
http://www.artima.com/weblogs/viewpost.jsp?thread=240808 http://www.artima.com/weblogs/viewpost.jsp?thread=240845
#!/usr/bin/env python2
from functools import wraps
class CommandInfo(object):
cmds = []
def __init__(self, shortname, longname, func):
self.shortname = shortname
self.longname = longname
self.func = func
class CommandDispatch(object):
def __init__(self, shortname, longname):
self.shortname = shortname
self.longname = longname
def __call__(self, func):
print("hello from CommandDispatch's __call__")
@wraps(func)
def wrapped_func(wself, *args, **kwargs):
print('hello from wrapped_func, args:{0}, kwargs: {1}'.format(args, kwargs))
func(wself, *args, **kwargs)
ci = CommandInfo
ci.cmds += [ci(shortname=self.shortname, longname=self.longname, func=func)]
return wrapped_func
@staticmethod
def func(name):
print('hello from CommandDispatch.func')
for ci in CommandInfo.cmds:
if ci.shortname == name or ci.longname == name:
return ci.func
raise RuntimeError('unknown command')
@CommandDispatch(shortname='co', longname='commit')
def commit(msg):
print('commit msg: {}'.format(msg))
commit('sample commit msg') # Normal call by function name
cd = CommandDispatch
short_f = cd.func(name='co') # Call by shortname
short_f('short sample commit msg')
long_f = cd.func(name='commit') # Call by longname
long_f('long sample commit msg')
class A(object):
@CommandDispatch(shortname='Aa', longname='classAmethoda')
def a(self, msg):
print('A.a called, msg: {}'.format(msg))
a = A()
short_fA = cd.func(name='Aa')
short_fA(a, 'short A.a msg')
long_fA = cd.func(name='classAmethoda')
long_fA(a, 'short A.a msg')
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