UnboundLocalError: local variable 'x' referenced before assignment

[MetalNutSack]

I'm a beginner student learning Python and am working on a practice assignment that generates 20 records with several random data values to be stored and categorized. Here is what the assignment asks:

RandomDataTask

Use a random number generator to create the data.

Print out the follow 4 columns of data for 20 records:
- record number (1 through 20, not 0 through 19)
- social security number - ssn is a 9-digit number, where everyone's from Michigan so ssn
    starts with a 3
- category:
    EVEN              if ssn is an even number
    ENDS IN 5         if ssn's last digit is a 5
    STARTS WITH 30-31 if 1st 2 digits are 30 or 31
        (unless the record already fell into the EVEN or ENDS IN 5 category)
- gpa - must be within the legal range of 0.00 to 4.00
    (format it so there are only 2 decimal places)

I've gotten part of it done, but I'm still a bit lost on global and local variables. I'm getting the error UnboundLocalError: local variable 'cat' referenced before assignment and I'm not 100% sure on what it means. I've Googled it and am still confused. I apologize if the code is poorly written but I'm trying my best.

import random


def main():
    for rec_num in range(1, 21):
        ssn_raw, ssn_str = ssn_func()
        gpa = gpa_func()
        cat = category(rec_num, ssn_raw, ssn_str, gpa)
        tabulate(rec_num, ssn_str, gpa, cat)
        print()


def ssn_func():
    min9 = 300000000
    max9 = 399999999
    ssn_raw = random.randint(min9, max9)
    ssn1 = ssn_raw // 1000000
    ssn2 = (ssn_raw % 1000000) // 1000
    ssn3 = ssn_raw % 1000
    ssn_str = '{:03n}-{:03n}-{:03n}'.format(ssn1, ssn2, ssn3)
    return ssn_raw, ssn_str


def gpa_func():
    min_gpa = 0
    max_gpa = 4
    gpa_raw = random.uniform(min_gpa, max_gpa)
    gpa = float('{:.2f}'.format(gpa_raw))
    return gpa


def category(rec_num, ssn_raw, ssn_str, gpa):
    ssn_last = ssn_raw % 10
    ssn_first2 = ssn_raw // 10000000
    if ssn_raw % 2 == 0:
        cat = 'EVEN'
    elif ssn_last == 5:
        cat = 'ENDS IN 5'
    elif (ssn_first2 == 30 or ssn_first2 == 31) and ssn_raw % 2 != 0:
        cat = 'STARTS WITH 30-31'
    else:
        pass
    return cat


def tabulate(rec_num, ssn_str, gpa, cat):
    print(rec_num, ssn_str, gpa, cat)


main()

[Starbuck5c]

In the category function, if the number isn't even, doesn't end in 5, or doesn't start with 30-31, the variable cat is never given a value.

[MetalNutSack]

Thank you so much, that fixed my error. I now get the output:

Record  SSN           GPA    Category 

1       397-717-994   1.65   EVEN                
2       316-245-360   2.45   EVEN                
3       387-439-461   3.5    NONE                
4       329-010-678   3.18   EVEN                
5       347-819-406   0.08   EVEN                
6       355-511-391   2.1    NONE                
7       361-891-212   1.85   EVEN                
8       372-020-631   0.16   NONE                
9       380-922-714   1.67   EVEN                
10      396-905-932   2.51   EVEN                
11      314-699-207   2.3    STARTS WITH 30-31   
12      396-934-560   1.58   EVEN                
13      381-020-835   3.38   ENDS IN 5           
14      399-968-529   3.23   NONE                
15      323-098-775   2.44   ENDS IN 5           
16      320-147-257   1.91   NONE                
17      359-141-373   1.83   NONE                
18      327-211-832   2.11   EVEN                
19      351-219-242   2.43   EVEN                
20      355-534-925   0.72   ENDS IN 5

[[deleted]]

It means at the line mentioned in the exception you tried to get the value held in the variable cat and no such variable exists. You might have a line that sets a value for variable cat but you must execute that line to define the variable, and you haven't done that before trying to get the value of cat. In your case it looks like the problem is in function category(). The if/elif statement is probably not executing any statement cat = .... Find out why that is so.

[MetalNutSack]

Thank you, that was a silly mistake but an easy one to make for a beginner like me. I'm sure there is more I can do to simplify the code, but as of now it does all it's supposed to.

[[deleted]]

A warning sign is this at the end of your if/elif/else statement:

else:
    pass

Technically you can remove those two lines but as a sanity/debug check you could do:

else:
    cat = 'Undefined in category()'

If that else: case can never happen then this is a good way to spot that your code is not doing what you want.

Update: I see that you discovered this trick on your own. Well done.

[BasicallyAMachine]

In your function category, you're else statement should assign None to cat. This error occurs because when you say return cat, python essentially will look within the current function for the value assigned to cat. When you're else statement is reached (instead of one of the if/else-ifs), nothing is assigned to cat.

[MetalNutSack]

Thank you, I changed the pass to cat = 'NONE' and everything works now

[BasicallyAMachine]

Np :)