Python: NameError while trying to hold a function in a variable and plugging the variable in to another function

Question

I was wondering if there was a way to store a function in a variable that includes a variable that has not yet been defined, and place that variable that holds the function in after the variable in the function has been defined. For example, I want this script below (this script is an example of the problem I am having in another script, yet the other script is way too long to include here) to print a number of days after you enter in weeks, however I get a NameError: name 'days_weeks' is not defined .

weeks = int(input("Enter a number of weeks"))
def print_weeks():
    print("that is %s days" % days_weeks)
x = print_weeks
def find_days():
    days_weeks = weeks * 7
    x
    x()
find_days()

Now, obviously, I can just plug print_weeks in find_days; however for the project I am working on I am using the first function (print_weeks in this case) dozens of times in my script, and the function is hundred of lines of code long, so I want to keep the function stored in a variable to make things way less sloppy. I have also tried to make days_week a global variable, yet the outcome of the code has stayed the same (or I just did it wrong). I have read a lot of other threads yet I have not been able to find an answer. Sorry if this has been confusing, but basically if anyone has a way to keep print_weeks in a variable and have this script print the days correctly it would be greatly appreciated.

x = print_weeks is unnecessary. Just use print_weeks where you would use x. — chepner
– chepner, Commented Feb 1, 2016 at 13:28

22degrees · Accepted Answer · 2016-02-01 03:06:15Z

1

You're getting the NameError because days_weeks is local to the function find_days, and not accessible to print_weeks. If you want days_weeks to be global, you need to change the find_days function.

def find_days():
    global days_weeks 
    days_weeks = weeks * 7
    x   
    x()

But, in general, it's better to pass the variables in an out of your functions, rather than rely on globals. In that case your code would look something like this:

def print_weeks(days):
    print("that is %s days" % days)
x = print_weeks

def find_days(f, Nweeks):
    days_weeks = Nweeks * 7
    f(days_weeks)

weeks = int(input("Enter a number of weeks"))
find_days(x,weeks)

edited Feb 1, 2016 at 3:06

answered Feb 1, 2016 at 2:50

22degrees

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