David Lemper wrote:
I'm a newbee trying 3.0 Please help with math.sqrt()
At the command line this function works correctly
>>> import math
n = input("enter a number > ")
s = math.sqrt(n)
An entry of 9 or 9.0 will yield 3.0
Yet the same code in a script gives an error message
Script1
import math
n = input("enter a number > ")
s = math.sqrt(n)
... TypeError : a float is required
>
Strangely the above code runs fine in version 2.5 ( ? ) ...
OK, here's what's going on:
"at the command line" in 2.X, the builtin function input reads a string
and returns the eval of that string. This is a bit of a safety issue.
I suspect when "it worked from the command line," you were using a 2.X
command line inadvertently. in 2.X, you'll get similar errors if you
use "raw_input" instead of "input".
The "input" function in 3.0 is the same as the "raw_input" function
in 2.X. I would suggest using:
import math
value = float(input("enter a number > "))
root = math.sqrt(value)
print('root(%s) == %s' % (value, root))
I avoid using single-letter variables except where I know the types
from the name (so I use i, j, k, l, m, n as integers, s as string,
and w, x, y, and z I am a little looser with (but usually float or
complex).
--Scott David Daniels
scott.dani...@acm.org
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