Julia RPN calculator algorithm ported from Python version
In case you don't already know this ...

Here is what the line [max(len(y) for y in x) for x in zip(*rp)] is doing.

Say that

rp = [('a', 'b', 'c', 'd'), ('aa', 'bbb', 'cccc', 'ddddd')]
unzipped_rp = zip(*rp) # [('a', 'aa'), ('b', 'bbb'), ('c', 'cccc'), ('d', 'ddddd')]


This code does almost the same as what the line above does ...

max_lengths = []

for x in unzipped_rp: 
    lengths = []
    for y in x:
        lengths.append(len(y))
    max_lengths.append(max(lengths))

print max_lengths


Output:
    [2, 3, 4, 5]