How do you get Python to detect for no input

Question

I\'m new to coding in python and I was filling out some code that required a number of inputs. One thing it asked for was for the program to perform an action if the user pr

Answer 1

I know this question is old, but I'm still sharing the solution to your problem as it could be a helpful hand to others. To detect no input in Python, you actually need to detect for "End of File" error. Which is caused when there is no input:
This can be checked by the following piece of code:

final=[]
while True:
    try:
         final.append(input())   #Each input given by the user gets appended to the list "final"
    except EOFError:
         break                   #When no input is given by the user, control moves to this section as "EOFError or End Of File Error is detected"

Hope this helps.

Answer 2

I'm new to python and was looking for a fix to a similar problem. I know this is a really old post but I thought I would have a go at it. If I understand your problem correctly and what you're trying to achieve, this works fine for me. (As long as you don't try and enter a letter!) I posted earlier but it wasn't right, sorry.

totalcoins = None
coinN = None
sum_total = range

while coinN != '0' and totalcoins != '0':
    coinN = input("Please enter first amount:   ")
    if coinN == "":
        print("You didn't enter anything")
    else:
        totalcoins = input("Please enter second amount   ")
        if totalcoins == "":
            print("You didn't enter anything")
        else:
            sum_total = int(coinN) + int(totalcoins)
            if sum_total in range(100):
                    print('Sorry, you only entered {} cents'.format(sum_total))
            else:
                if sum_total == 100:
                    print('The sum of {0} and {1} is = 1 rand     '.format(coinN, totalcoins, sum_total))
            if sum_total >=100:
                print('The sum of {0} and {1} is = {2} rand   '.format(coinN, totalcoins, sum_total))
                print("\n")

Answer 3

Just another tips:

In python you don't need to do equality test for empty string. Instead please use truth value testing. That is more pythonic.

if not coinN:

Truth value testing covers the following test:

• None
• False
• zero of any numeric type, for example, 0, 0L, 0.0, 0j.
• any empty sequence, for example, '', (), [].
• any empty mapping, for example, {}.
• instances of user-defined classes, if the class defines a nonzero() or len() method, when that method returns the integer zero or bool value False. 1

Example:

>>> s = ''
>>> if not s:
...     print 's is empty'
...
s is empty
>>>

Answer 4

Actually an empty string would be

""

Instead of

" "

The latter is a space character

Edit
A few other notes

1. Don't use input as your variable name that is a Python keyword

2. Comparing equality uses == instead of =, the latter is an assignment operator, it attempts to modify the value of the left-hand side.

Answer 5

EDIT:

what about something like this:

 try:
     coinN = input("Enter next coin: ")
     if coinN.isdigit(): # checks whether coinN is a number
         if coinN == "" and totalcoin == rand:
             print("Congratulations. Your calculations were a success.")
         if coinN == "" and totalcoin < rand:
             print("I'm sorry. You only entered",totalcoin,"cents.")
     else:
         raise ValueError

 except ValueError:
     print("Invalid Input")
 else:
     totalcoin = totalcoin + int(coinN) # convert coinN to int for addition