从函数中的函数调用变量

Question

Quick question. I first defined a function prc_chgd that ultimately gives me a variable ans , but as an intermediate step gives me the variable price . Now, I want to write a subsequent function hdg , that using the same order of inputs, used the intermediate variable price to calculate something else. Unfortunately, I don't know how :S

def prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    price = xyz
    ans   = price*abc

def hedge(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    from prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y) import price
    ans = price*xxxx

the point is that the functions are two separate excercises within a notebook assignment, and I might have to recalculate the preceding function with new inputs (in the same order though), and only choose the defined variable price for my calculation.

Thanks a bunch in advance!

Answer 1

I cannot completely follow, but I think your xyz is some mysterial combination of p0, ta, ya etc.

In this case, you should put the price calculation into a separate function such as

def calc_price(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    return xyz # calculated with these inputs

def prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    price = calc_price(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y)
    ans = price * abc

def hedge(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    price = calc_price(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y)
    ans = price * xxxx

If you want to avoid to have your price be computed twice, you could also do

def calc_price(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    return xyz # calculated with these inputs

def prc_chgd(price):
    ans = price * abc

def hedge(price):
    ans = price * xxxx

and leave it to the caller how often calc_price() is called.

Answer 2

You can return more than one value from your function if you want like this:

def prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    price = xyz
    ans   = price*abc
    return price, ans


def hedge(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
    price, ans = prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y)
    ans = price*xxxx

Answer 3

Function that returns multiple return values should yield in python:

def prc_chgd(p0, ta, ya, tb, yb, cb, delta1_y, delta2_y):
   price = xyz
   yield price
   ans   = price*abc
   yield ans

You can yield as many values as you like. Then you can iterate over all the answers in a for loop:

for total in prc_chgd(1,2,3,4,5,6,7,8):
   print total

First it will print the price, then price*abs. Since the 2 functions belong together, I recommend to use a class.