Test for number?

[Dr. Pastor]

In the following code I would like to ascertain
that x has/is a number. What the simplest TEST should be?
(Could not find good example yet.)
---
x=raw_input('\nType a number from 1 to 20')
if TEST :
Do_A
else:
Do_B
---
Thanks for any guidance.

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[Hardcoded Software]

Dr. Pastor wrote:

In the following code I would like to ascertain
that x has/is a number. What the simplest TEST should be?
(Could not find good example yet.)
---
x=raw_input('\nType a number from 1 to 20')
if TEST :
Do_A
else:
Do_B
---
Thanks for any guidance.

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To test if it *is* a number, the solution is pretty simple (s.isdigit()
or an int(s) in a try..except ValueError), but if you want to test if
it is or *has* a number, I think that the simplest solution would be a
regexp:

import re
re_has_digit = re.compile(r'\d+')
try:
digits = re_has_digit.findall(input)[0]
number = int(digits)
print "%d is a number." % number
except IndexError:
print "'%s' has no number in it." % input

I didn't try it, but it should work.

[George Sakkis]

Dr. Pastor wrote:

In the following code I would like to ascertain
that x has/is a number. What the simplest TEST should be?
(Could not find good example yet.)
---
x=raw_input('\nType a number from 1 to 20')
if TEST :
Do_A
else:
Do_B
---
Thanks for any guidance.

x=raw_input('\nType a number from 1 to 20')
try:
x = int(x)
if x<1 or x>20: raise ValueError()
except ValueError:
Do_B
else:
Do_A
If you want to distinguish between the two error cases (not a number vs
number not in [1,20]), handle the second one as "Do_C" instead of
raising ValueError.

HTH,
George

[Neil Cerutti]

On 2006-09-04, George Sakkis <ge***********@gmail.comwrote:

Dr. Pastor wrote:

>In the following code I would like to ascertain that x has/is
a number. What the simplest TEST should be? (Could not find
good example yet.)
---
x=raw_input('\nType a number from 1 to 20')
if TEST :
Do_A
else:
Do_B
---
Thanks for any guidance.

x=raw_input('\nType a number from 1 to 20')
try:
x = int(x)
if x<1 or x>20: raise ValueError()
except ValueError:
Do_B
else:
Do_A

If you want to distinguish between the two error cases (not a
number vs number not in [1,20]), handle the second one as
"Do_C" instead of raising ValueError.

Is the original value of x available in Do_B and Do_A, or will it
have been clobbered before getting there?

--
Neil Cerutti

[George Sakkis]

Neil Cerutti wrote:

On 2006-09-04, George Sakkis <ge***********@gmail.comwrote:

x=raw_input('\nType a number from 1 to 20')
try:
x = int(x)
if x<1 or x>20: raise ValueError()
except ValueError:
Do_B
else:
Do_A

If you want to distinguish between the two error cases (not a
number vs number not in [1,20]), handle the second one as
"Do_C" instead of raising ValueError.

Is the original value of x available in Do_B and Do_A, or will it
have been clobbered before getting there?

In Do_A, x will be an integer between 1 and 20. In Do_B, it depends; if
the original input cannot be converted to an int, it will be preserved,
otherwise x will be an integer (lower than 1 or larger than 20).

George

[Neil Cerutti]

On 2006-09-05, George Sakkis <ge***********@gmail.comwrote:

Neil Cerutti wrote:

>On 2006-09-04, George Sakkis <ge***********@gmail.comwrote:

x=raw_input('\nType a number from 1 to 20')
try:
x = int(x)
if x<1 or x>20: raise ValueError()
except ValueError:
Do_B
else:
Do_A

If you want to distinguish between the two error cases (not a
number vs number not in [1,20]), handle the second one as
"Do_C" instead of raising ValueError.

Is the original value of x available in Do_B and Do_A, or will
it have been clobbered before getting there?

In Do_A, x will be an integer between 1 and 20. In Do_B, it
depends; if the original input cannot be converted to an int,
it will be preserved, otherwise x will be an integer (lower
than 1 or larger than 20).

Thanks. I infer from this that in the case that int(x) raises
ValueError, that x is guaranteed to be unmodified.

--
Neil Cerutti
22 members were present at the church meeting held at the home
of Mrs. Marsha Crutchfield last evening. Mrs. Crutchfield and
Mrs. Rankin sang a duet, The Lord Knows Why. --Church Bulletin Blooper