checking if character is in string Python

Question

from decimal import *
errors = "abcdffghijklmnopqrstuvwxyz?><:;\|{}[]"
purchase_price = Decimal(input("Please enter the price of your item"))
while purchase_price in errors:
    print("Please enter the price of your item ex: 123.45")
    break
else:

I'm having trouble checking if a character or characters in the errors var is being input.

When input is anything that is not a number

The Output is :

Traceback (most recent call last):
  File "C:/Users/Chris/PycharmProjects/Tax Calculator/main.py", line 4, in <module>
    purchase_price = Decimal(input("Please enter the price of your item"))
decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]

If a character is there I would like to write a loop to give them another opportunity to to re-enter the price.

Why Decimal? Convert the input to float do like this, float(input("Please enter the price of your item")) It would cause an error if illegal char is entered — Sailesh Kotha
– Sailesh Kotha, Commented Feb 5, 2015 at 14:05
sailesh, just thought I'd note again that floats are not a good way to handle money, since usually good accuracy is important :) — Ryan O'Donnell
– Ryan O'Donnell, Commented Feb 5, 2015 at 14:06

Ryan O'Donnell · Accepted Answer · 2015-02-05 14:04:49Z

1

If you want the input to be a number, I'd suggest making it a float and handling the exception if you cannot parse it:

try:
    purchase_price = float(input("Please enter the price of your item"))
except (ValueError, TypeError) as e:
    pass # wasn't valid, print an error and ask them again.

Though, please note that floats are not a good way to accurately handle money! This is a huge deal! You need to search online to find a good solution: http://code.google.com/p/python-money/

answered Feb 5, 2015 at 14:04

Ryan O'Donnell

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2 Comments

Shilo Over a year ago

Hey thanks for the help. I've got the money library up and running in place of Decimal. Could you explain the except portion for me? I got lost when I saw as e

Ryan O'Donnell Over a year ago

That passes the exception object to e so you can properly log and handle the exception as you need to.

sarveshseri · Accepted Answer · 2015-02-05 14:12:01Z

0

from decimal import *

def ask():
    input_str = input("Please enter the price of your item");
    try:
        number = Decimal( imput_str )
        return number
    except( InvalidOperation, ValueError, TypeError ) as e:
        return ask()


number = ask()

answered Feb 5, 2015 at 14:12

sarveshseri

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