# [Tutor] Do loop in Python

Tue Nov 29 09:51:45 CET 2011

Thank you so much. This script and all information was totally helpful
and actually helped me for the next step of my work as well.

Have a great time.....
Sue

On Fri, Nov 25, 2011 at 10:44 PM, Andreas Perstinger
<andreas.perstinger at gmx.net> wrote:
> On 2011-11-25 14:46, stm atoc wrote:
>>
>> Here is the new version of the program:
>>
>> zvalues = [-200]  # starting value
>> hvalues = [10]  # starting value
>> increments = [1, 1, 1, 1, 1, 1, 1, 1]
>> for N in increments:
>>        h = hvalues[-1] - N
>>        hvalues.append(h)
>>        z = zvalues[-1] + h
>>        zvalues.append(z)
>>        height = arange((z)*dz,0,dz)
>
>
> There is no "arange" in python. Could it be that you use numpy and import it
> with "from numpy import *"?
>
>>        for z,when in enumerate(height):
>
>
> I'm pretty sure this line doesn't do what you expect it to do. You have a
> sequence (a numpy array) named "height" and after calling "enumerate" you
> get a list of tuples in the form of [(0, height[0]), (1, height[1]), ...].
> Now the for-loop iterates over this list and assigns "z" to the first value
> of the tuple (the index-values) and "when" to the second (the values from
> "height"). You later never use "when" but just use "z". If you really want
> that, the "enumerate" is completly unnecessary and you could just use "for z
> in range(len(height))". But I'm not sure if numpy arrays work with "len()".
>
>
>>            nuh.append(0.001 * exp(-0.005*(z+200.0))*dz) #turbulence
>> diffusivity m**2/s
>>            nu.append(num + nuh[z])
>>
>> The story is like this:
>> I should define layers and thickness and see how the diffusion profile
>> changes over the z.
>> height (or depth) of the total thickness or 'z'.
>> I basically, define 'z' in 10 layers and each layer is called  ' N' .
>> Difference between each layer is 'h', which is equal 10 micrometer.
>> Now, what I like to do is the modification of nu based on each zvalue
>> In fact, for each 'zvalue' o'z' step, I need to calculate a different
>> value for 'nu' based on the available equation in the program.
>>
>> BUT, I am not sure, exactly, how to add the new do loop of z inside
>> another loop of nu.
>
>
> For me your explanations are still too confusing. Could it be that you are
> thinking way too complicated?
>
> My guess is you want to have a range of material thicknesses (from 1 to 200
> micrometers in 10 micrometer-steps) and then you want from each thickness 10
> different layers, right?
>
> import math # you should always tell us which modules you import
> num = 0.05 # some constant
> nu = [] # list of resulting values
> h = 10.0 # height of one layer
> thickness = range(0, 210, 10) # a list from 0 to 200 with step 10 (0, 10,
> 20, ..., 190, 200)
> layers = range(1,11) # a list from 1 to 10
> for t in thickness:
>  for l in layers:
>    z = t + h * l # I'm not sure if you want to add or subtract the layer
> thickness
>    nu = num + (0.01 * math.exp(-0.05 * (z + 200.0)))
>
> This will result in a big one-dimensional list where you calculate for each
> thickness the nu-value for 10 layers. Am I close?
> I'm still not sure about the steps and the height of the layers. I also
> wonder if it wouldn't be better to use a two-dimensional list.
>
>
>> I have done this way as well (the other way around):
>>
>> height = arange((z)*dz,0,dz)
>> for z,when in enumerate(height):
>>     for N in increments:
>>        h = hvalues[-1] - N
>>        hvalues.append(h)
>>        z = zvalues[-1] + h
>>        zvalues.append(z)
>>        nuh.append(0.001 * exp(-0.005*(z+200.0))*dz) #turbulence
>> diffusivity m**2/s
>>        nu.append(num + nuh[z])
>>
>> but still no sign of 'nu changes' over 'z'!
>
>
> As Charles has already mentioned, the values for "nu" are very similar (they
> start beginning to differ just at the seventh digit after the comma). How do
> you further process this values? If you plot them what's your scale?
>
> Bye, Andreas
>
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