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POndarray field names for both row and column?
 

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  1. POndarray field names for both row and column?
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    <p>I'm a computer science teacher trying to create a little gradebook for myself using NumPy. But I think it would make my code easier to write if I could create an ndarray that uses field names for both the rows and columns. Here's what I've got so far:</p> <pre><code>import numpy as np num_stud = 23 num_assign = 2 grades = np.zeros(num_stud, dtype=[('assign 1','i2'), ('assign 2','i2')]) #etc gv = grades.view(dtype='i2').reshape(num_stud,num_assign) </code></pre> <p>So, if my first student gets a 97 on 'assign 1', I can write either of:</p> <pre><code>grades[0]['assign 1'] = 97 gv[0][0] = 97 </code></pre> <p>Also, I can do the following:</p> <pre><code>np.mean( grades['assign 1'] ) # class average for assignment 1 np.sum( gv[0] ) # total points for student 1 </code></pre> <p>This all works. But what I <strong>can't</strong> figure out how to do is use a student id number to refer to a particular student (assume that two of my students have student ids as shown):</p> <pre><code>grades['123456']['assign 2'] = 95 grades['314159']['assign 2'] = 83 </code></pre> <p>...or maybe create a second view with the different field names?</p> <pre><code>np.sum( gview2['314159'] ) # total points for the student with the given id </code></pre> <p>I know that I could create a dict mapping student ids to indices, but that seems fragile and crufty, and I'm hoping there's a better way than:</p> <pre><code>id2i = { '123456': 0, '314159': 1 } np.sum( gv[ id2i['314159'] ] ) </code></pre> <p>I'm also willing to re-architect things if there's a cleaner design. I'm new to NumPy, and I haven't written much code yet, so starting over isn't out of the question if I'm Doing It Wrong.</p> <p>I <em>am</em> going to be needing to sum all the assignment points for over a hundred students once a day, as well as run standard deviations and other stats. Plus, I'll be waiting on the results, so I'd like it to run in only a couple of seconds.</p> <p>Thanks in advance for any suggestions.</p>
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