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- ArgFreeze
class ArgFreeze |
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a callable class that freezes (remembers) arguments to a function.
Note: this is not the implementation of a closure. The callable
object only remembers its parameters, not global variables. Note also
that it just remembers plain values and references. It doesn't do
a deep copy of objects that are given as parameters.
The remembered parameters can be overwritten with parameters given
when the ArgFreeze functor is actually called. The remembered parameter
work like defaults.
Here are some examples:
>>> def test(arg1,arg2,arg3):
... print "arg1:",arg1," arg2:",arg2," arg3:",arg3
Here, ArgFreeze returns a callable object that
has remembered the 3 arguments that were given at
it's creation:
>>> c=ArgFreeze(test,1,2,3)
We can call c with no arguments at all, then the
three arguments given at it's creation are taken:
>>> c()
arg1: 1 arg2: 2 arg3: 3
We can override the first argument with a different value:
>>> c(10)
arg1: 10 arg2: 2 arg3: 3
We can override the first two arguments with different values:
>>> c(10,20)
arg1: 10 arg2: 20 arg3: 3
We can override all three arguments with different values:
>>> c(10,20,30)
arg1: 10 arg2: 20 arg3: 30
I we try to specify too many arguments, we would get an error:
> > c(10,20,30,40)
Traceback (most recent call last):
...
TypeError: test() takes exactly 3 arguments (4 given)
(note: no doctest here since python3 produces a different error message)
You can also use named parameters like here:
>>> c=ArgFreeze(test,arg1=1,arg2=2,arg3=3)
You can then call with no parameters at all, in this case
the default parameters are taken:
>>> c()
arg1: 1 arg2: 2 arg3: 3
You can specify a single parameter with a different value:
>>> c(arg2=20)
arg1: 1 arg2: 20 arg3: 3
However, you must use the same style as in the ArgFreeze
creation. For example, using an unnamed parameter here doesn't
work since ArgFreeze remembers the value for "arg1" to be 1. If
the function is called with "10", ArgFreeze cannot know, that this
should override "arg1" and in the end we get an error:
>>> c(10)
Traceback (most recent call last):
...
TypeError: test() got multiple values for keyword argument 'arg1'
Remember when calling an ArgFreeze object to use the same style
you took at it's creation. Here is an example that works:
>>> c=ArgFreeze(test,1,2,arg3=3)
Calling without arguments works, of course:
>>> c()
arg1: 1 arg2: 2 arg3: 3
Setting a different value for the first (unnamed) parameter
works, too:
>>> c(10)
arg1: 10 arg2: 2 arg3: 3
Setting a different value for the third (named) parameter
works:
>>> c(arg3=30)
arg1: 1 arg2: 2 arg3: 30
Combining both, works:
>>> c(10,arg3=30)
arg1: 10 arg2: 2 arg3: 30
But specifying the third parameter unnamed (different to
the creation of the ArgFreeze object) does not work:
>>> c(10,20,30)
Traceback (most recent call last):
...
TypeError: test() got multiple values for keyword argument 'arg3'
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Methods defined here:
- __call__(self, *args, **kw)
- Implementation of the object call function.
- __init__(self, func, *args, **kw)
- The constructor of the callable object.
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