Need help with a simple function

[WorldPark]

Hi,

I am totally new to Python and programming. However, I tryed to create a simple function, which is not working. Please help.

def money(capital, years, added_yearly, interest):
    a = 0
    while a < years:
        capital = (capital+added_yearly)*interest
        a = a+1
        return (capital, years)

money(33000, 5, 3000, 1.1)
print("Your capital after %s years will be %s" % (years, capital))

When I am trying to run this code with PowerShell, it give me the error:

NameError: name 'years' is not defined

even though I am returning the values with my function. What am I doing wrong?

[woooee]

Include the complete trackback so we know which line contain the error.

[perfringo]

You didn’t assign names to function result. There are no reference to object returned. You also can’t access names in function namespace from outside.

[WorldPark]

Include the complete trackback so we know which line contain the error.

The error is in line 9.

[perfringo]

Your problem is on this row:

money(33000, 5, 3000, 1.1)

Where does value returned by function goes? There is no references to this returned object, therefore garbage collector destroys it and it's gone!

Your function returns tuple, so you can unpack it (f-strings, so Python >= 3.6 is required):

def money(capital, years, added_yearly, interest):
    a = 0
    while a < years:
        capital = (capital+added_yearly)*interest
        a = a+1
        return (capital, years)
 
capital, years = money(33000, 5, 3000, 1.1)
print(f"Your capital after {years} years will be {capital}")

Output:
Your capital after 5 years will be 39600.0

Alternatively you can unpack it when printing (I reversed order of returned values):

def money(capital, years, added_yearly, interest):
    a = 0
    while a < years:
        capital = (capital+added_yearly)*interest
        a = a+1
        return (years, capital)
 
print("Your capital after {} years will be {}".format(*money(33000, 5, 3000, 1.1)))

Output:
Your capital after 5 years will be 39600.0

You can also return namedtuple which enables doing some nice descriptive stuff.

However, while in interactive interepreter and not running file you can use underscore (interpreter remembers last value by assigning it with name _):

In [1]: def money(capital, years, added_yearly, interest): 
   ...:     a = 0 
   ...:     while a < years: 
   ...:         capital = (capital+added_yearly)*interest 
   ...:         a = a+1 
   ...:         return (years, capital) 
   ...:                                                                       

In [2]: money(33000, 5, 3000, 1.1)                                            
Out[2]: (5, 39600.0)

In [3]: "Your capital after {} years will be {}".format(*_)                   
Out[3]: 'Your capital after 5 years will be 39600.0'

As a sidenote - this is not the way to calculate capital. You will get wrong result.