add dictionary comprehension

Author: rmccorm4

comprehension/dictionary/README.md

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+# List Comprehension
+This directory is here to show the Speed Difference between using 
+Dictionary Comprehension vs. a For Loop to create a dictionary
+
+## Executing
+In a UNIX terminal, run:
+
+
+```
+time python dict-loop.py
+
+real	0m3.087s
+user	0m2.762s
+sys	0m0.324s
+```
+
+```
+time python dict-comp.py
+
+real	0m2.581s
+user	0m2.252s
+sys	0m0.328s
+```
+
+
+Here we see that the dictionary comprehension is about 20% faster
+than the for loop method. Again, this is a case-by-case scenario,
+but generally the Dictionary comprehension will probably be faster.
+There are probably cases where dictionary comprehension is slower, 
+but at the end of the day, comprehensions are generally used for
+more concise code rather than for speed.

comprehension/dictionary/dict-comp.py

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+d = {i : i**2 for i in range(1, 10_000_001)}

comprehension/dictionary/dict-loop.py

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+d = {}
+
+for i in range(1, 10_000_001):
+	d[i] = i**2