CODEWITHSUNDEEP
pythonfunction
Cupitor
Cupitor

Reputation: 11657

How to define sum of multiple arbitrary functions?

Suppose I have a list of functions

f1(x,y),f2(x,y),....

How can I define the function below: 

z(x,y)=f1(x,y)+f2(x,y)+...

I want to be able to specify x later. So if somebody puts the y=c value, I want the z function to become a function of x! In the simple case when you you have one function, f, and you want to make f(x,y) to be a function of x only by specifying y=c you can use:

z=lambda x:f(x,c)

but the thing is such a method won't work for more than one function!

Upvotes: 0

Views: 261

Answers (4)

gepoch
gepoch

Reputation: 711

Tweaking the previous answers, we can throw in functools.partial to create the desired behavior.

We can do a partial function call (similar to the haskell construct) to produce new functions from incompletely applied functions. Check it out:

from functools import partial

funcs = [lambda x, y: x + y] * 10 # a list of ten placeholder functions.

def z(functions, x, y):
    return sum(f(x, y) for f in functions)

a = partial(z, funcs, 1)
# 'a' is basically the same as: lambda y: z(funcs, 1, y)
print a # <functools.partial object at 0x7fd0c90246d8>
print a(1) # 20
print a(2) # 30
print a(3) # 40

More here: http://docs.python.org/2/library/functools.html#functools.partial

Upvotes: 2

2rs2ts
2rs2ts

Reputation: 11046

What if you have other arbitrary functions? What if you want to sum any old number of functions?

def funcSum(x, y, *funcs):
    return sum((func(x,y) for func in funcs))

funcSum(x, y, f, g, h)

Arbitrary numbers of arguments gets a little more complex...

Upvotes: 1

perreal
perreal

Reputation: 98078

Can be useful for 10s of functions:

def z(x,y,functions):
    return sum(F(x,y) for F in functions)

So you can use it like:

z(x,y,(f,g,h))

Or if the number of functions comes from a list:

z(x,y,list_of_functions)

Upvotes: 5

Imre Kerr
Imre Kerr

Reputation: 2428

Assuming you have your functions in a list functions:

z = lambda x, y : sum((f(x, y) for f in functions))

Upvotes: 2

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