[Tutor] Loop over floating point values

[spir]

On 12/01/2013 10:03 AM, Amit Saha wrote:
> Hello,
>
> Much to my disbelief, I realized I hadn't written a program in Python
> as far as I can recall which required me to do something like this, in
> psuedocode:
>
> x = 0.1
>
> for i = 0 to x step 0.01
> # do something with i
> end i
>
> Simply stated, I want to start from say a value, 0 and go upto 0.1 in
> increments of 0.01.  I don't want to create a list with the values
> hard-coded and then iterate over it, and hence I would use a while
> loop instead:
>
> x = 0.1
> while i < x:
>     # do something with i
>     i += 0.01
>
> I think this is one case, where you definitely cannot do this with a
> for loop assuming the following restrictions:
>
> - Do not create a list of the floating point values as i=[0.01, 0.02,
> 0.03..] - either like that or by using a suitable mathematical formula
> combined with a list comprehension
> - Use numpy's linspace() to create the list for you
>
>
> Thoughts?

There is a general solution for this (a typical school problem ;-), maybe the 
reason why we rarely meet it in practice!). However, watch the issues with 
binary floats mentionned by Steven.

# loop from x0 to x1 with step dx, total n passes
x0, x1, dx, n = -0.3, 0.8, 0.2, 6
for i in range(n):
     x = x0 + dx * i
     print(x)