Problem in understanding Python list comprehensions

Question

What does the last line mean in the following code?

import pickle, urllib                                                                                                 


        

Answer 1

Firstly, you need to put http:// in front of the URL, ie:

handle = urllib.urlopen("http://www.pythonchallenge.com/pc/def/banner.p")

An expression [e for e in a_list] is a list comprehension which generates a list of values.

With Python strings, the * operator is used to repeat a string. Try typing in the commands one by one into an interpreter then look at data:

>>> data[0]
[(' ', 95)]

This shows us each line of data is a tuple containing two elements.

Thus the expression e[1] * e[0] is effectively the string in e[0] repeated e[1] times.

Hence the program draws a banner.