# Issue

This Content is from Stack Overflow. Question asked by Samuel Muldoon

There is a tool in the `functools` library named `partial`.

`functools.partial` allows us to specify some of the inputs a function without specifying all of them.

You can transform …
`funky_function(x1, x2, x3, x4, x5)`
into something like…
`funky_function(1, 2, x3, x4, x5)`

That is…

• Input argument `x1` gets assigned the number `1`
• Input argument `x2` gets assigned the number `2`
• Inputs `x3`, `x4`, `x5` are still not assigned anything.
``````from functools import *
from inspect import *

def funky_function(x1, x2, x3, x4, x5, /):
return ", ".join(" ".join(str(x).split()) for x in [x1, x2, x3, x4, x5])

funky_function = partial(funky_function, 1, 2)

result = funky_function(3, 4, 5)

print("return value from `funky_function(3, 4, 5)` is:", result)
print("signature of `funky_function` is:", signature(funky_function))
``````

My question is, how do we make a decorator?

``````@partialize(1, 2)
def funky_function(x1, x2, x3, x4, x5, /):
return ", ".join(" ".join(str(x).split()) for x in [x1, x2, x3, x4, x5])

result = funky_function(3, 4, 5)
``````

Look at the function signature below of `partial.partial(func)`:

``````functools.partial(func, /, *args, **keywords)
``````

The function is the left and the arguments on the right.

The following two pieces of code are equivalent:

``````@decorate(1, 2)
def f():
pass
###################################
def f():
pass
f = decorate(1, 2)(f)
``````

So, `partial` is not a good decorator if you want to enter arguments first, and enter the function second.

How do we make a decorator which takes in the arguments first, and later accepts the function to-be-decorated?

# Solution

Something like the following works:

``````from functools import *
from inspect import *

def partialize(*args, **kwargs):
def partialize_helper(old_func):
new_func = partial(old_func, *args, **kwargs)
return new_func
return partialize_helper

@partialize(1, 2)
def funky_function(x1, x2, x3, x4, x5, /):
return ", ".join(" ".join(str(x).split()) for x in [x1, x2, x3, x4, x5])

##########################################################################

funky_function = partialize(1, 2)(funky_function)

##########################################################################

result = funky_function(3, 4, 5)
print("valued returned by funky_function(3, 4, 5)".ljust(50), result)
print("str(funky_function) ==".ljust(50), str(funky_function))
print("Signature == ".ljust(50), signature(funky_function))
``````

Console output is as follows:

``````valued returned by funky_function(3, 4, 5)         1, 2, 3, 4, 5
str(funky_function) ==                             functools.partial(<function funky_function at 0x000001C99759E200>, 1, 2)
Signature ==                                       (x3, x4, x5, /)
``````

``` This Question was asked in  StackOverflow by  Samuel Muldoon and Answered by Samuel Muldoon It is licensed under the terms of
CC BY-SA 2.5. - CC BY-SA 3.0. - CC BY-SA 4.0.```