How can i catch any error caused by unset module variable? - python-3.x

Question

So I have this function list and showlist but i need to catch any error caused by an unset module variable. can someone help me whats the first thing i should do?
this is my code at the moment
import csv
filep #filepath
menulist = []
def list():
"""Function to read the csv file, create a nested list
and return the list that is sorted based on calories
in the ascending order."""
global menulist
menulist = [] #store items
with open(filep) as csv_file: #read file
reader = csv.reader (csv_file, delimiter=',')
next(reader, None)
for row in reader:
row[2] = int(row[2].strip())
row[1] = float(row[1].strip())
if row[2]> 100 and row[2] <200:
menulist.append(row)
menulist.sort(key=lambda x: x[-1])
def show_list():#Function to display menu
global menulist
for i in range(len(menulist)):
print ('%-4d%-20s%-15s%-15s' %(i + 1, menulist[i][0], menulist[i][2], menulist[i][1]))
list()
show_list()
for example, if the variable file is not set before the list() is called, the function needs to catch an error and prints an appropriate comment

Answer 1

You are using a built-in function name as your function name. Which is not considered as a good practice in Python. It replaces the built-in function list() which is used to create a list. And you need to define a variable before you can use it.
Here's how you can catch the error and print an appropriate comment, with the variable defined:
import csv
filep = str(input("Enter the file name with path : ")) # filepath
menulist = []
def calorieList():
"""Function to read the csv file, create a nested list
and return the list that is sorted based on calories
in the ascending order."""
global menulist
menulist = [] # store items
with open(filep) as csv_file: # read file
reader = csv.reader(csv_file, delimiter=",")
next(reader, None)
for row in reader:
row[2] = int(row[2].strip())
row[1] = float(row[1].strip())
if row[2] > 100 and row[2] < 200:
menulist.append(row)
menulist.sort(key=lambda x: x[-1])
def show_list(): # Function to display menu
global menulist
for i in range(len(menulist)):
print("%-4d%-20s%-15s%-15s" % (i + 1, menulist[i][0], menulist[i][2], menulist[i][1]))
try:
calorieList()
except FileNotFoundError:
print("Enter a valid file path.")
show_list()

Answer 2

I assume you meant filep by the file variable.
If you try to access filep before it is set, your program should raise NameError: name 'filep' is not defined.
But if you want to raise a custom error message, you can just use a try-except block as follows:
import csv
filep #filepath
menulist = []
def list():
"""Function to read the csv file, create a nested list
and return the list that is sorted based on calories
in the ascending order."""
global menulist
menulist = [] #store items
try:
with open(filep) as csv_file: #read file
reader = csv.reader (csv_file, delimiter=',')
next(reader, None)
for row in reader:
row[2] = int(row[2].strip())
row[1] = float(row[1].strip())
if row[2]> 100 and row[2] <200:
menulist.append(row)
except NameError:
raise ValueError("Your custom message here")
menulist.sort(key=lambda x: x[-1])
def show_list():#Function to display menu
global menulist
for i in range(len(menulist)):
print ('%-4d%-20s%-15s%-15s' %(i + 1, menulist[i][0], menulist[i][2], menulist[i][]))
list()
show_list()