"NameError: name 'day_time' is not defined" error in Python3.8

Question

I am making a program which tells the part of the day by the time entered.

My code:

user_day = input("What's the time? ")

if user_day >= 20 and user_day <= 24:
    day_time = "Night"

elif user_day >= 24 and user_day <= 12:
    day_time = "Morning"

elif user_day >= 12 and user_day >= 17:
    day_time = "Noon"

elif user_day >= 17 and user_day >= 20:
    day_time = "Evening"

But I am getting this error:

if day_time == 1 and user_weather == plus:
NameError: name 'day_time' is not defined

Please help me out.

Answer 1

You need to declare day_time outside the context of if blocks if you wish to use it later on.

Like so, for example:

user_day = input("What's the time? ")

day_time = None

if user_day >= 20 and user_day <= 24:
    day_time = "Night"

elif user_day >= 24 and user_day <= 12:
    day_time = "Morning"

elif user_day >= 12 and user_day >= 17:
    day_time = "Noon"

elif user_day >= 17 and user_day >= 20:
    day_time = "Evening"

Answer 2

• The issue is, user_day is a string when entered as an input.
  • Because it's a string, it doesn't meet any of the conditions, and therefore, day_time remains undefined.
    • Wrap the input in a try-except block to check that the input is a proper data type. In this case, str type that can be converted to an int or float.
  • It must be converted to a int or float depending on if you're going to accept only hours or fractional hours.
• user_day should be in a while True loop to continue asking for a time until a valid numeric input is received.
• Finally, the code can be written more efficiently, by properly ordering the conditions from smallest to largest, for this case.
  • user_day will trickle down to the correct condition.

while True:
    try:
        user_day = int(input("What's the hour on a 24-hour scale? "))
    except ValueError:  # checks for the correct data type; maybe someone will spell the hour
        print('Please enter the hour as a numeric value')
    
    if (user_day >= 24) or (user_day < 0):  # 24 and over or less than 0 are invalid times
        print('Please enter a valid time')
    else:
        break  # break when there's valid input

if user_day < 12:
    day_time = 'Morning'
elif user_day < 17:
    day_time = 'Noon'
elif user_day < 20:
    day_time = 'Evening'
else:
    day_time = 'Night'
    
print(day_time)

Use np.digitize

• Return the indices of the bins to which each input value belongs.
• Use the value returned by np.digitize to index the correct value from day_time

import numpy as np

while True:
    try:
        user_day = int(input("What's the hour on a 24-hour scale? "))
    except ValueError:  # checks for the correct data type; maybe someone will spell the hour
        print('Please enter the hour as a numeric value')
    
    if (user_day >= 24) or (user_day < 0):  # 24 and over or less than 0 are invalid times
        print('Please enter a valid time')
    else:
        break  # break when there's valid input

day_time = ['Morning', 'Evening', 'Noon', 'Night']
idx = np.digitize(user_day, bins=[12, 17, 20])
    
print(day_time[idx])

Answer 3

You need to define day_time in an else statement so that when neither of the existing conditions meet, day_time will still have a value.

Also, you need to convert the user's input into an integer before you can use the <, >, etc operator on it with a string:

user_day = int(input("What's the time? "))

if user_day >= 20 and user_day <= 24:
    day_time = "Night"

elif user_day >= 24 and user_day <= 12:
    day_time = "Morning"

elif user_day >= 12 and user_day >= 17:
    day_time = "Noon"

elif user_day >= 17 and user_day >= 20:
    day_time = "Evening"

else:
    day_time = "Unknown"