A problem with str VS int.

[dn]

On 10/12/23 15:42, Steve GS via Python-list wrote:
>   If I enter a one-digit input or a three-digit number, the code works but if I enter a two digit number, the if statement fails and the else condition prevails.
> 
>         tsReading = input("   Enter the " + Brand + " test strip reading: ")
>          if tsReading == "": tsReading = "0"
>          print(tsReading)
>          if ((tsReading < "400") and (tsReading >= "0")):
>              tsDose = GetDose(sReading)
>              print(tsReading + "-" + tsDose)
>              ValueFailed = False
>          else:
>              print("Enter valid sensor test strip Reading.")
> 
> I converted the variable to int along with the if statement comparison and it works as expected.
> See if it fails for you...

It works as expected (by Python)! This is how strings are compared - 
which is not the same as the apparently-equivalent numeric comparison.

Think about what you expect from the code below, and then take it for a 
spin (of mental agility):

values = [ 333, 33, 3, 222, 22, 2, 111, 11, 1, ]
print( sorted( values ) )
strings = [ "333", "33", "3", "222", "22", "2", "111", "11", "1", ]
print( sorted( strings ) )


The application's data appears numeric (GetDose() decides!). 
Accordingly, treat it so by wrapping int() or float() within a 
try-except (and adjusting thereafter...).


"But wait, there's more!"
(assuming implement as-above):

if 0 <= ts_reading < 400:

1 consistent 'direction' of the comparisons = readability
2 able to "chain" the comparisons = convenience
3 identifier is PEP-008-compliant = quality and style

-- 
Regards,
=dn