On 04/06/2013 06:00 PM, Soliman, Yasmin wrote:
I have two questions on these simple programs:
>
> 1st why does this loop keep repeating after I enter 'Quit'?
>
> import calendar
> m = raw_input(“Enter a year: “)
> while m != “Quit”:
> if calendar.isleap(int(m)):
> print “%d is a leap year” % (int(m))
> else:
> print “%d is not a leap year” % (int(m))
>
>
> 2nd How can I make this program not crash when a user enters a non
integer?
>
> m = raw_input(“Enter an integer: “)
> while not m.isdigit():
> m = raw_input(“Enter an integer: “)
> num = int(m)
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In pseudocode, you need to do something like this:
- loop forever
inp = user input
if inp is Quit: break
try to convert inp to int
if success:
print if inp is leap year or not
else:
print error
I have written a small function that handles a more general case of
asking user for a certain kind of input (e.g. number, text, yes/no, etc)
and keeps asking it until the answer in right format is given. Here it
is:
import re
def simpleinp(pattern, prompt="> ", convert=None, errmsg="Invalid
Input", blank=False):
"""Keep asking user for input until it matches `pattern`."""
if pattern == "%d": pattern = "\d+"; convert = int
if pattern == "%s": pattern = ".+"
while True:
i = input(prompt).strip()
if blank and not i: return None
if re.match('^'+pattern+'$', i):
return convert(i) if convert and i else i
else:
print(errmsg)
# print( simpleinp("%d", "integer: ") )
# print( simpleinp("%s", "string: ") )
# print( simpleinp(".*", "string or blank: ") )
# print( simpleinp("[ynYN]", "y/n: ") )
HTH, -m
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