On 2017-10-09, John Black <jbl...@nopam.com> wrote:
> I want to make sure I understand what this line is doing:
>
>> oldprint = print
>
> Experimenting, I find this is not a rename because I can use both
> function names.
Right it's not _changing_ a name. It's _adding_ a name.
> It looks it literally copies the function "print" to
> another function called "oldprint".
No, it binds a new name of 'oldprint' to the function to which 'print'
is bound. It does not create a second function, nor does it remove
the binding of the name 'print' to that function. It just adds a
second name that's also bound to that function.
> But now, I have a way to modify the builtin funciton "print" by
> referencing oldprint. Without oldprint, I have no way to directly
> modify print?
Well... you can still access the builtin print via the module that
contains it:
>>> def print(*args, **kw):
... __builtins__.print(*args, sep='', **kw)
...
>>> print(1,2,3)
However, anytime you find yourself using double underscore stuff you
should think to yourself "I should find a better way to do that."
> def print(*args, **kw):
> print(*args, sep='', **kw)
>
> meaning print calls print (itself) with sep=''. But this failed and I
> guess the reason is that it would keep calling itself recursively adding
> sep='' each time?
Yep.
Just define a new function with a new name:
def myprint(*args, **kw):
print(*args, sep='', **kw)
Redefining builtins is just going get you sworn at down the road a
bit. If not by yourself, then by somebody else...
--
Grant Edwards grant.b.edwards Yow! Used staples are good
at with SOY SAUCE!
gmail.com
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