decimal numbers

[Laurent Pointal]

luke.geelen at gmail.com wrote:

> hello,
> i have been working on a python resistor calculator to let my class show
> what you can do with python. now i have a script that makes the more
> speekable value of the resistance (res)
> 
> #if len(str(res)) > 9:
> #  res2 = res / 1000000000
> #  print "de weerstand is %s,%s giga ohms" % (res2)
> #elif len(str(res)) > 6:
> #  res2 = res / 1000000
> #  print "de weerstand is %s,%s Mega ohm" % (res2)
> #elif len(str(res)) > 3:
> #  res2 = res / 1000
> #  print "de weerstand is", res2,"kilo ohm"
> #elif len(str(res)) < 4:
> #  res2 = res
> #  print "de weerstand is", res2,"ohm"
> 
> i commented it because it doesn't work (yet), when i have a resistance of
> 9.9 Giga ohms it says it is 9 giga ohms. it seems to work with natural
> number, anyway of using decimals insted so that it says : the resistance
> is 9.9 Giga Ohms instead of 9 ?

Seem you are using Python2, if res is an integer the division by an integer 
values produce an integer result (changed in Python3), so you loose the 
decimal part.

Try dividing by floating point numbers, like res2 = res / 1000.


Note: should take a lok at the log10() function from math module.

(with Python3)

In [1]: from math import log10

In [2]: r = 132828378723

In [3]: int(log10(r))
Out[3]: 11

In [4]: r / 10**int(log10(r))
Out[4]: 1.32828378723

A+
Laurent.