Python - UnboundLocalError: local variable “ID” referenced before assignment

Question

Id, conf = recognizer.predict(gray[y:y+h,x:x+w]
def hour(cn):
   for z in range(9,17):  
      if now.hour == z:
         worksheet(cn, str(z)+":00")

def identify(number):
   sht = gc.open("Test")
   wks3 = sht.worksheet("NAMES")
   b = wks3.acell('B'+str(number)).value
   a = wks3.acell('A'+str(number)).value
   if(Id == a and conf<65):
     print(Id, conf)
     Id = str(b)
     Time = time.ctime()
     hour(number)
   elif(conf>64):
     print(conf)
     Id = "Unknown"

for m in range(2,100):

     identify(m)

The above code is being used for facial recognition, I copied what I felt was necessary, it is not the entire code.

I'm trying create a function which I want to call back in a for loop

What am I doing wrong? I've been looking t this for 6 hours now, and anything I try doesn't seem to work.

I get a message back saying "UnboundLocalError: local variable 'Id' referenced before assignment"

It's impossible because I'm assigning with:

a = wks3.acell('A'+str(number)).value

So it grabs the ID number from the google spread sheet and checks if it is equaled to that, can someone tell me where I'm going wrong here?

Answer 1

def identify(number):
   sht = gc.open("Test")
   wks3 = sht.worksheet("NAMES")
   b = wks3.acell('B'+str(number)).value
   a = wks3.acell('A'+str(number)).value
   #because you did, Id = ? 
   if(Id == a and conf<65):
     print(Id, conf)
     Id = str(b)
     Time = time.ctime()
     hour(number)
   elif(conf>64):
     print(conf)
     Id = "Unknown"

Because you did, variable Id isn't passed as any parameter or global/local variable or as an argument to existing class.

If Id was parameter:

def identify(number,Id): 

If Id was global variable:

def identify(number):
    global Id  

If Id was local variable:

def identify(number):
    id = None # or some other data type  

And if Id was argument from some class:

some_class.Id 

In short you referenced Id before it was initialised. This is rookie mistake and there is some stuff where you can actually init a variable in if elif else statement but you need to trow a none of above logic of the rule.

if True: Id = 2; elif False: Id = 3; else: Id =0 #this is pseudocode, don't paste it in.

Also have in mind that next variable is also Unbound conf

---

EDIT:

Often to avoid this problem we write code like this:

def somefunction(parm1,parm2... ): 

    # global variables : description for variable stack is optional
    global var1,var2 # if needed  

    #local variables  
    var3,var4 = None;  
    var5 = 'something else'  

    #in body functions : functions inside functions or just general program functions 
    def a(... ): return ...  

    #body : actually what function/program does.   

    # returning , finishing statement.