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Iterating with Basic For Loops
3:39Use basic Python for loops to iterate over your sequence data.
Welcome back, we're going to dive right
into something we can actually do with
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sequences, iteration.
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You might have heard this term before or
a similar term, iterable.
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Basically, iterating means
looping over a sequence.
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If something is iterable it
means it can be looped over.
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All Python sequences are iterable,
they can all be looped over.
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And that's what we'll be
talking about in this video,
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basic iteration with for loops.
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Basic iterating over Python sequences can
be done with what we call a for loop, or
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more descriptively, a for in loop.
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A for loop in Python is just a way to
perform an action on every element in
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a sequence, one by one, in order.
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The for loop will continue to loop or
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iterate on its own until it's worked its
way through every element in the sequence.
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You can think of a for
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loop as saying for each element
in a sequence, do this action.
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Where the element will be referenced
by a variable name of your choice, and
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the action is whatever code
is inside the for loop block.
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Consider a basic string.
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To iterate over each letter in this
string, that is, to access all of
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the letters individually, one by one,
and in order, we can use a for loop.
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The pseudo code becomes real code.
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Where letter is a variable I created
to reference the current element
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in the my_name sequence on each
iteration through the loop.
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All right,
let's take this example a little further,
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feel free to follow along with me.
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You'll have an opportunity to try this
on your own in a workspace in just
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a little while.
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Down on my command line tool, I'm gonna
start up the python interpreter by typing
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python or python3 if I want to
use the newest version of python.
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I'll recreate the my_name
variable which held the string.
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And then I'll write a for
loop that iterates over it and
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prints out each letter.
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To write the for loop,
I write the word for.
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Then I create a variable that will store
each element as the for loop iterates.
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I'll call it letter, then the word in, and
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then the name of the sequence
which is my_name.
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Now I'll add a print statement.
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Now I'll hit Enter to run it.
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Cool, we can see here that the loop
iterated six times, once for
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every letter in my name.
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On each loop, it printed out the letter
that was being accessed in that iteration.
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Now you try,
open up the attached workspace.
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Inside the groceries.py file,
you'll see a Python list called groceries.
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Pause the video here and write your
own for loop that iterates through
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all the elements in the groceries list and
prints them out.
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When you think you've got it, or
if you've gotten stuck, unpause and
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I'll show you the solution.
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Okay, how did it go?
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Let's exit the console and jump to
the groceries.py file to see the solution.
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To exit the interpreter, I use Ctrl + D.
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And then I'll clear the console
to free up some space.
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Okay, up in our file we have
the groceries list with six elements.
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To write the for loop, I use keyword for.
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Then I'll create the loop variable,
I'll call it item.
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And then the word in and
the name of the sequence, groceries.
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On the next line, I'll write
a print statement that prints out
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the current item.
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And that's it.
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If we save and
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run this, we'll see each element in
the grocery list printed on its own line.
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Let's take a look Cool,
there's our grocery list.
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Join me in the next video to learn
about how we can take our loops
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to the next level.
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