How can I make a class that can be converted into an int?

[Matthew Wilson]

What are the internal methods that I need to define on any class so that
this code can work?

c = C("three")

i = int(c) # i is 3

I can handle the part of mapping "three" to 3, but I don't know what
internal method is called when int(c) happens.

For string conversion, I just define the __str__ method. What's the
equivalent for int? For float, too, while I'm at it?

TIA

Matt

--
A better way of running series of SAS programs:
http://overlook.homelinux.net/wilson...asAndMakefiles

[faulkner]

__int__
__long__
__float__
Matthew Wilson wrote:

What are the internal methods that I need to define on any class so that
this code can work?

c = C("three")

i = int(c) # i is 3

I can handle the part of mapping "three" to 3, but I don't know what
internal method is called when int(c) happens.

For string conversion, I just define the __str__ method. What's the
equivalent for int? For float, too, while I'm at it?

TIA

Matt

--
A better way of running series of SAS programs:
http://overlook.homelinux.net/wilson...asAndMakefiles

[Tim Chase]

What are the internal methods that I need to define on any class so that

this code can work?

c = C("three")

i = int(c) # i is 3

I can handle the part of mapping "three" to 3, but I don't know what
internal method is called when int(c) happens.

For string conversion, I just define the __str__ method. What's the
equivalent for int? For float, too, while I'm at it?

Is it too unkind to say it's semi-obvious?

>>class Impersonator(object):

.... def __str__(self): return "I'm a string"
.... def __int__(self): return 42
.... def __float__(self): return 3.14159
....

>>c = Impersonator()
float(c)

3.1415899999999999

>>int(c)

42

>>str(c)

"I'm a string"

You say you can handle the conversion of "three" to 3, so I leave
that implementation of __int__(self) to you... :)

-tkc

[Mikael Olofsson]

Matthew Wilson wrote:

What are the internal methods that I need to define on any class so that
this code can work?

c = C("three")

i = int(c) # i is 3

From Python Reference Manual, section 3.4.7 Emulating numeric types:

__complex__( self)
__int__( self)
__long__( self)
__float__( self)
Called to implement the built-in functions complex(), int(),
long(), and float(). Should return a value of the appropriate type.

/MiO

[Peter Otten]

Matthew Wilson wrote:

What are the internal methods that I need to define on any class so that
this code can work?

c = C("three")

i = int(c) # i is 3

I can handle the part of mapping "three" to 3, but I don't know what
internal method is called when int(c) happens.

>>class C(object):

.... def __int__(self): return 42
....

>>int(C())

42

For string conversion, I just define the __str__ method. What's the
equivalent for int? For float, too, while I'm at it?

http://docs.python.org/ref/numeric-types.html

Peter