"UnboundLocalError: local variable referenced before assignment" after an if statement

Before I start, I’d like to note that I can’t actually test this since your script reads data from a file that I don’t have.

‘T’ is defined in a local scope for the declared function. In the first instance ‘T’ is assigned the value of ‘data[2]’ because the conditional statement above apparently evaluates to True. Since the second call to the function causes the ‘UnboundLocalError’ exception to occur, the local variable ‘T’ is getting set and the conditional assignment is never getting triggered.

Since you appear to want to return the first bit of data in the file that matches your conditonal statement, you might want to modify you function to look like this:

def temp_sky(lreq, breq):
    for line in tfile:
        data = line.split()
        if ( abs(float(data[0]) - lreq) <= 0.1 and abs(float(data[1]) - breq) <= 0.1):            
            return data[2]
    return None

That way the desired value gets returned when it is found, and ‘None’ is returned when no matching data is found.

The other answers are correct: You don’t have a default value. However, you have another problem in your logic:

You read the same file twice. After reading it once, the cursor is at the end of the file, so trying to read it again returns nothing and the loop is never entered. To solve this, you can do two things: Either open/close the file upon each function call:

def temp_sky(lreq, breq):
    with open("/home/path/to/file",'r') as tfile:
        # do your stuff

This has the disadvantage of having to open the file each time. The better way would be:

tfile.seek(0)

You do this after your for line in tfile: loop. It resets the cursor to the beginning so the next call will start from there again.

Related questions:

• Iterating on a file doesn't work the second time
• Why a file is empty after reading it?

FWIW: I got the same error for a different reason. I post the answer here not for the benefit of the OP, but for the benefit of those who may end up on this page due to its title… who might have made the same mistake I did.

I was confused why I was getting “local variable referenced before assignment” because I was calling a FUNCTION that I knew was already defined:

def job_fn(job):
  return job + ".job"

def do_something():
  a = 1
  b = 2
  job_fn = job_fn("foo")

do_something()

This was giving:

UnboundLocalError: local variable 'job_fn' referenced before assignment

Took me a while to see my obvious problem: I used a local variable named job_fn which masked the ability to see the prior function definition for job_fn.

I was facing same issue in my exercise. Although not related, yet might give some reference. I didn’t get any error once I placed addition_result = 0 inside function. Hope it helps! Apologize if this answer is not in context.

user_input = input("Enter multiple values separated by comma > ")

def add_numbers(num_list):
    addition_result = 0
    for i in num_list:
        addition_result = addition_result + i
    print(addition_result)

add_numbers(user_input)

Contributing to ferrix example,

class Battery():

    def __init__(self, battery_size = 60):
        self.battery_size = battery_size
    def get_range(self):
        if self.battery_size == 70:
            range = 240
        elif self.battery_size == 85:
        range = 270

        message = "This car can go approx " + str(range)
        message += "Fully charge"
        print(message)

My message will not execute, because none of my conditions are fulfill therefore receiving ” UnboundLocalError: local variable ‘range’ referenced before assignment”

def get_range(self):
    if self.battery_size <= 70:
        range = 240
    elif self.battery_size >= 85:
        range = 270

To Solve this Error just initialize that variable above that loop or statement. For Example var a =""