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Readability, Style, and Turtles
CSCI-UA.002
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Style
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How the code is formatted; how it looks visually
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Variable naming
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Use of idioms
Why is style important? →
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Style
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How the code is formatted; how it looks visually
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Variable naming
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Use of idioms
Why is style important? →
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You'll probably spend more time reading code than writing it:
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code you've written
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example code from books, specifications, forums, etc.
other people's code (collaboration, inherited code, etc.)
If everyone follows the same style, it'll be easier to read and
edit existing programs = Maintainability
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Conventions
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Most programming languages have established conventions
for style.
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Usually programming teams (or companies) will also have a
set of conventions, or coding style guide.
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The goal is readability and maintainability
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Python has a published proposal laying out good guidelines
https://www.python.org/dev/peps/pep-0008/
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Conventions to Follow
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Consistency! Whatever conventions you use, keep them
consistent across the entire project, or at least within a file.
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4 space indentation (automatic in IDLE) →
if answer == 5:
print('correct')!
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Use blank lines to separate groups of related code to enhance
readability
x = 2
y = 5
print("x plus y is ...")
print(x + y)
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More Conventions
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Surround operators with whitespace in expressions
# do this:
count = count + 1
# *not* this:
count=count+1
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only use lowercase letters in variables names
# do this:
count = 0
# *not* this:
Count=0
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separate words in variable names using underscores
# do this:
my_count = 1
# *not* this:
mycount = 1
myCount = 1
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Idioms
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An idiom can be:
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A saying or expression whose meaning is not obvious from
its individual parts
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An expression that is natural to a language
Generally native speakers, or people who know the language
well, know the idioms
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it's raining cats and dogs
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hace mucho frío
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les carottes sont cuites
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Programming Idioms
Similar to Natural Languages, an idiom in a programming
language is:
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a common task, computation, or construct that's expressed
in a way that's unique, peculiar to or encouraged by the
particular programming language in use
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understood by all who know the language and its
conventions
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usually are the best (most efficient) way in that language to
do that thing
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Not necessarily formally specified and usually not the only
way to do it.
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Turtle Graphics
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Turtle is a Python module…
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Allows you to draw programmatically (think of a virtual pen
plotter)
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Commands are given to a movable pen
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That pen can move and draw on a two dimensional plane
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The pen is called a turtle!
It's essentially a Python implementation of another language
called Logo
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created in the mid 60's
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built on theory of constructionist learning (learn by
experimentation)
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Turtle Graphics
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Imagine you have a turtle
hanging out on the beach
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imagine further that it's a
robotic turtle that you can
give commands to
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move forward
turn around
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as it moves, it leaves tracks
on the ground
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turtle graphics simulates
this (seriously)
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Turtle Graphics
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We can draw by writing code
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That code is analogous to the commands that we would give
the turtle (or pen, or pointer, or whatever)
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move forward
turn around
but in addition, we can also
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change colors
ask for user input
etc.