Calling a variable from a function in a function

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!

Where is hedge called from? You'll need to return price from prc_chgd if you want it to be used elsewhere. — Carcigenicate
– Carcigenicate, Commented Mar 19, 2020 at 13:28

glglgl · Accepted Answer · 2020-03-19 13:33:02Z

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.

Huskell · Accepted Answer · 2020-03-19 13:30:49Z

1

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

answered Mar 19, 2020 at 13:30

Huskell

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1 Comment

germany Over a year ago

looks good in theory, but in my assignment the first function is evaluated on the output of prc_chgd, and will only take one value. thus, if I return two values in the function body, I get an error message from my assignment saying it expects only one value as output.

Bart Mensfort · Accepted Answer · 2020-03-19 13:38:55Z

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.

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