I’m having an issue with the scope of the distance() function. The function code is given, but when I call this function, I run into errors. When I ignore the function and calculate the distance manually with the lines:
smallest_distance = math.sqrt((x - x_0)**2 + (y - y_0)**2)
and
distance = math.sqrt((x - x_2)**2 + (y - y_2)**2)
the code works fine. So the only issue here is when I use the defined function. But why…?
Screen Link:
My Code:
# provided input
x = 100
y = 100
# answer to this input: LEADBETTERS II
from csv import reader
import math
def distance(x_1, y_1, x_2, y_2):
return math.sqrt((x_1 - x_2)**2 + (y_1 - y_2)**2)
def closest_restaurant(x, y):
# Create a list from the CSV file (header is excluded)
opened_file = open('restaurants.csv')
read_file = reader(opened_file)
rows = list(read_file)[1:]
# Initialize the coordinates/distance and the restaurant name
x_0 = int(rows[0][-2])
y_0 = int(rows[0][-1])
smallest_distance = math.sqrt((x - x_0)**2 + (y - y_0)**2)
# smallest_distance = distance(x, y, x_0, y_0) #doesn't work. Why???
closest_name = ''
# Loop over the rows and compute the smallest distance
for row in rows[1:]:
x_2 = int(row[-2])
y_2 = int(row[-1])
distance = math.sqrt((x - x_2)**2 + (y - y_2)**2)
# distance = distance(x, y, x_2, y_2)
# Same problem again. I can't use the distance(0) method here, why not???
if distance < smallest_distance:
smallest_distance = distance
closest_name = row[0]
return closest_name
closest_restaurant(x, y)
What I expected to happen:
I expected to be able to use the distance() function to calculate the distance.
What actually happened:
I get an error message telling me that the variables resulting from calling the distance() function are undefined. I called this function twice: at line 21 and line 30. So it means the function call didn’t work. But am I not doing the calculation within the function scope? I don’t understand why I can’t call the function here.
<ipython-input-1-34e8ca735ac0> in closest_restaurant(x, y)
21 y_0 = int(rows[0][-1])
22 # smallest_distance = math.sqrt((x - x_0)**2 + (y - y_0)**2)
---> 23 smallest_distance = distance(x, y, x_0, y_0) #doesn't work. Why???
24
25 closest_name = ''
UnboundLocalError: local variable 'distance' referenced before assignment
I guess I don’t have a good understanding of function scope yet. Any help would be appreciated.
This was my first message on the board, Dataquest noob here 
I checked all other 4 topics on this problem, so I hope this question is not redundant.
