Duck Typing

[srijit]

Hello All,
I have been seeing this term "duck typing" for quite sometime now. It
will be nice if one of us can give an example in Python demonstrating
duck typing and/or link to some Python references.

Regards,
Srijit

 

[John Roth]

Hello All,
I have been seeing this term "duck typing" for quite sometime now. It
will be nice if one of us can give an example in Python demonstrating
duck typing and/or link to some Python references.

Why in the world would anyone want to do such a thing? I hadn't
heard the term until you just brought it up, so a quick Google defined
it. AFAICT, it's simply a cute name that's applied to a very common
technique in languages that don't use static typing.

In other words, if you need a file-like object, and someone passes
you an object, your options are either to just use it (and handle the
exceptions if it doesn't really support the proper interface) or use
reflection to see if it has methods with the proper name and number
of parameters, and then be prepared to handle the exceptions when
they don't do what you expect.

Six of one, half a dozen of the other.

John Roth

 

[Irmen de Jong]

I have been seeing this term "duck typing" for quite sometime now. It
will be nice if one of us can give an example in Python demonstrating
duck typing and/or link to some Python references.

Is this helpful: http://www.razorvine.net/python/PythonLanguageConcepts
(paragraph 'dynamic typing') ?

--Irmen de Jong

 

[Oren Tirosh]

Hello All,
I have been seeing this term "duck typing" for quite sometime now. It
will be nice if one of us can give an example in Python demonstrating
duck typing and/or link to some Python references.

class Duck:
def quack(self):
print "Quack!"

class MeWearingSillyDuckOutfit:
def quack(self):
print "ummm... Quack!"

def make_it_quack(obj):
obj.quack()

a = Duck()
b = MeWearingSillyDuckOutfit()
make_it_quack(a)
make_it_quack(b)

 

[Steve Holden]

class Duck:
def quack(self):
print "Quack!"

class MeWearingSillyDuckOutfit:
def quack(self):
print "ummm... Quack!"

def make_it_quack(obj):
obj.quack()

a = Duck()
b = MeWearingSillyDuckOutfit()
make_it_quack(a)
make_it_quack(b)

exquacktly [ducks and runs]

regards

 

[Peter Hansen]

exquacktly [ducks and runs]

^^^^^

Steve, did you even _know_ you did this? You're sick!

-Peter

 

[Irmen de Jong]

exquacktly [ducks and runs]

^^^^^

Steve, did you even _know_ you did this? You're sick!

-Peter

people are currently turning their heads to me to see why I
suddenly bursted out in laughter

--Irmen

 

[Steve Holden]

exquacktly [ducks and runs]

^^^^^

Steve, did you even _know_ you did this? You're sick!

-Peter

Aah, I see, you think I'm stupid.

Of course I knew - without the bracketed afterthought it would hardly have
been worth posting.

I'll send you a bill ;-)

regards

 

[Peter Hansen]

exquacktly [ducks and runs]

^^^^^

Steve, did you even _know_ you did this? You're sick!

-Peter

Aah, I see, you think I'm stupid.

No, I just knew Irmen was asleep at his keyboard. ;-)

Of course I knew - without the bracketed afterthought it would hardly have
been worth posting.

I'll send you a bill ;-)

If you make it a twenty, would that be a "sawduck"?

-Peter

 

[Oren Tirosh]

class Duck:
def quack(self):
print "Quack!"

class MeWearingSillyDuckOutfit:
def quack(self):
print "ummm... Quack!"

def make_it_quack(obj):
obj.quack()

a = Duck()
b = MeWearingSillyDuckOutfit()
make_it_quack(a)
make_it_quack(b)

exquacktly [ducks and runs]

class Run:
def quack(self):
print "QUACK!"

ducks = [Duck() for i in range(10)]
runs = [Run() for i in range(10)]
apply(make_it_quack, ducks+runs)

Oren

 

[Steve Holden]

Steve Holden wrote:

exquacktly [ducks and runs]
^^^^^

Steve, did you even _know_ you did this? You're sick!

-Peter

Aah, I see, you think I'm stupid.

No, I just knew Irmen was asleep at his keyboard. ;-)

Of course I knew - without the bracketed afterthought it would hardly have
been worth posting.

I'll send you a bill ;-)

If you make it a twenty, would that be a "sawduck"?

You'll never beat me at this game. After all, I did write "Web Programming
in Python" ;-)

regards