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POHow to use classes derived from Python's list class
 

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  1. POHow to use classes derived from Python's list class
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    <p>This is a followup to question 912526 - <a href="https://stackoverflow.com/questions/912526/how-do-i-pass-lots-of-variables-to-and-from-a-function-in-python">How do I pass lots of variables to and from a function in Python?</a>.</p> <p>There are lots of variables that need to get passed around in the program I'm writing, and from my previous question I understand that I should put these variables into classes, and then pass around the classes.</p> <p>Some of these variables come in repetetive sets - for a thin film calculation I need to track the optical properties (index of refraction, absorption, thickness, etc) for a number of layers.</p> <p>Is the best way to store variables like this to create a class derived from a Python list to store the set of classes which each hold the variables for a single layer? And then put the functions that deal with the set of layers in class derived from the list, and the functions that deal with a specific layer in that class? Is there a better way to do this with a single class? </p> <p>Using the two class approach in the following example, I'm able to set things up so that I can access variables using statments like</p> <pre><code>n1 = layers[5].n </code></pre> <p>This is the best way to do this, right?</p> <pre><code>#Test passing values to and from functions class Layers(list): def add(self,n,k,comment): self.append( OneLayer(n,k,comment) ) def input_string(self): input_string = [] for layer in self: vars = layer.input_string() for var in vars: input_string.append( var ) return input_string def set_layers(self,results): for layer,i in enumerate(self): j = i*layer.num_var layer.set_layer( *results[j:j+2] ) class OneLayer(object): def __init__(self,n,k,comment): self.n = n self.k = k self.comment = comment def input_string(self): return [['f','Index of Refraction',self.n], ['f','Absorption',self.k],['s','Comment',self.comment]] def set_layer(self,n,k,comment): self.n = n; self.k=k; self.comment = comment def num_var(self): return 3 if __name__ == '__main__': layers = Layers() layers.add(1.0,0.0,'This vacuum sucks') layers.add(1.5,0.0,'BK 7 Glass') print layers[0].n print layers.input_string() layers[1].set_layer(1.77,0.0,'Sapphire') print layers.input_string() </code></pre> <p>I get the following output from this test program:</p> <pre><code>1.0 [['f', 'Index of Refraction', 1.0], ['f', 'Absorption', 0.0], ['s', 'Comment', 'This vacuum sucks'], ['f', 'Index of Refraction', 1.5], ['f', 'Absorption', 0.0], ['s', 'Comment', 'BK 7 Glass']] [['f', 'Index of Refraction', 1.0], ['f', 'Absorption', 0.0], ['s', 'Comment', 'This vacuum sucks'], ['f', 'Index of Refraction', 1.77], ['f', 'Absorption', 0.0], ['s', 'Comment', 'Sapphire']] </code></pre>
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    1. CODo you really need a `Layers` class that inherits from `list`? Just use a list instead.
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      1. USNikhil Chelliah
 

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