CODEWITHSUNDEEP
pythonpython-3.x
Webber
Webber

Reputation: 23

On Shortening Code

I'm quite new to programming in Python. I have always written my int inputs like the following example to ensure a user inputs an int. This is a specific example I have in my code that I'm sure I can shorten and thus learn for future projects.

This ensures a three digit number is input by creating a loop that breaks when a three digit number is entered.

while 1 == 1:
  print("Input a 3 digit number")
    #The try statement ensures an INTEGER is entered by the user
    try:
      x = int(input())
      if 100 <= x < 1000:
        break
      else:
        print()
    except ValueError:
      print()

Upvotes: 2

Views: 224

Answers (3)

Rafael
Rafael

Reputation: 7242

You can do something like this:

while True:
    x = input("Input a 3 digit number: ")
    if x.isdigit() and 100 <= int(x) <= 999:
        break

isdigit() checks whether the string consists of digits only (won't work for floats). Since Python uses short-circuiting to evaluate boolean expressions using the operator and, the second expression 100 <= int(x) <= 999 will not be evaluated unless the first (x.isdigit()) is true, so this will not throw an error when a string is provided. If isdigit() evaluates to False, the second expression won't be evaluated anyway.

Another option is the following:

condition = True
while condition:
    x = input("Input a 3 digit number: ")
    condition = not (x.isdigit() and 100 <= int(x) <= 999)

Upvotes: 5

Rob Bricheno
Rob Bricheno

Reputation: 4653

Here's a fun alternative that avoids the need for a break or an exception at all:

x = ""
while not x.isdigit() or (100 > int(x) or int(x) > 999):
    x = input("Input a 3 digit number")
x = int(x)

Upvotes: 2

Aaron
Aaron

Reputation: 11075

If you want to handle the two different failures separately (not an int vs not 3 digit) you could do something like this:

while True:
    try:
        x = int(input('enter a 3 digit number'))
        assert(100 <= x <= 999)
    except ValueError: print('not an int')
    except AssertionError: print('int not 3 digit')
    else: break

It's not worlds shorter, but it is still very readable, and gives extra information to the user. Additionally if your intent is to make it re-usable, you should make it a function (just replace break with return x and add def funcname(): to the beginning (don't forget indentation)).

Upvotes: 3

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