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range  # We're going to use a "range" to learn how to mock-up some data quickly.


    

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help(range)  # Ranges are a good example of a function with optional parameters, so look at its help.


    

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range(20)  # Calling range directly (under Python 3) creates a range object and not a list as you might want/expect


    

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list(range(20))  # Simply wrap the range in a list to turn it into one.


    

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list(range(1, 21))  # Use what we learned from the help to offset the zero-based index.


    

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list(range(1, 21, 3))  # Just for fun, pick every third item from the list (step by stride)


    

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alist = list(range(1, 21))  # Okay, we're going to want 1 through 20 referenced by a variable named alist.
alist


    

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[alist]  #If you but square brackets around a list, you have a list inside a list.


    

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[x for x in alist]  # But if you add "x for x in" at the beginning, you have a normal list again... but one you can mess with.


    

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[aline for aline in alist]  # For starters, "x for x in" is arbitrary. You can name it to make more sense.


    

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['foo' for aline in alist]  # If you use a string instead of the iteration variable name, you get the string that many times.


    

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['foo-%s' % aline for aline in alist]  # Using string replacement, you can combine strings with variable values.


    

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[alist for aline in alist]  # And you can actually use the entire list for each line in a list for an easy matrix.


    

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[tuple(alist) for aline in alist]  # As we recall, tuples are more meory efficient for this use.


    

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(tuple(alist) for aline in alist)  # And while it's way beond the scope of this intro, this is the most efficient use:


    

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row_generator = (tuple(alist) for aline in alist)  # This technique can step through billions of records memory efficiently.
for row in row_generator:
    print(row)


    

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list_of_tuples = [tuple(alist) for aline in alist]  # Let's make a simple list of tuples for our next step.
list_of_tuples