Dictionary Struggles in Python (Part 2)

Today I want to continue discussion from last time about problems I had coding a dictionary application in Python.

Despite the fix already described, I remained puzzled with regard to speed of the original program. I added some #debug lines for timing purposes and also to display progress:

The last line prints out as ~50 seconds, but it takes an additional ~100 seconds before the graph renders and execution concludes. What’s taking the additional 100 seconds? And why does it take even 50 seconds to loop through the dictionary? The dictionary has 717 key-value pairs, which doesn’t seem like that much. These questions remain unanswered.

Iterating over the dictionary is not uniform. It goes slowly until about 200-300 and then prints up to 500 in an instant, to 700 and done. The last 400 or so are lightning fast while the first 200-300 are really slow. I get similar results with this code in Spyder and Jupyter Notebook.

The if statement explains this lack of uniformity. The program should go faster for keys > 250 since nothing is to be done. Only qualifying keys are to be plotted.

Is the conditional statement evaluating dictionary order or value of the key (not to be confused with the key’s corresponding value)? Consider the dictionary {3:29, 8:32, 1:16}. Keys under 10 include the first and second one (or 0th and 1st one given zero-indexing). If this referred to order, then all keys would be under 10 since only the dictionary has only three keys. This doesn’t make logical sense since dictionaries are unordered.

That keys are evaluated in terms of inherent value is verified by this code:*

As I run this code over and over several times, I get a varying number of keys > 5 in the last line. If the conditional referred to order, then five keys > 5 would always be identified (i.e. the sixth, seventh, eighth, ninth, and tenth).

The moral of this story is hard to say. I definitely don’t want to plot every point every time. I want to iterate over each point and plot if it qualifies. Even better, probably, would be plotting all points at once. That might also save more time. I need to study the code closer to figure out how to do that.

* — Line 2 should read: “generate 10 random numbers between 1 and 20.”