Python Basics

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Python Basics
Tom LeFebvre
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Python Language

• Very High-Level Language
• Scripting Language (no compiling)
• Simple syntax
• Easy to Learn/Use
• Slow execution

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Indentation

• Python uses indentation to identify blocks of
  code
• Might be difficult to get used to
• Code is more readable

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Code Comments

• Code comments are identified with the
  symbol
• Example

Print the value print The value is, value
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Statements

• The if statement has the syntax

if condition1 doSometing elif condition2
doSomethingDifferent elif condition3
doAnotherThing else doSomethingElse
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Statements (cont.)

• The for loop has the syntax
• The range statement is very useful

for iterator in list doSomethingWithTheIterat
or
range(0,10) is the same as 0, 1, 2, 3, 4,
5, 6, 7, 8, 9 for i in range(10) print i
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The def Statement

• The def statement starts a method.

def myMethod print myMethod executing.
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Data Structures - Lists

• List a (mixed) collection of objects
• Lists are mutable
• Lists may be nested 1, 2, 3 , 6, 7

myList hello, 2, 10.24
myList2 20.48 print myList hello, 2,
20.48
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Data Structures - Tuples

• Tuple an immutable (mixed) collection of objects

cityInfo (Boulder, (40.0, -105.0)) cityName,
location cityInfo copy out components print
cityName Boulder print location (40.0, -105.0)
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Data Structures - Dictionaries

• Dictionary non-ordered collection referred to by
  a key.

key data
myDict joe (Joseph Smith, Private,
5226677), sam(Samuel
Jones, Sergeant, 5124989),
bob(Robert Doe, General, 7689098),

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Other Peoples Code

• Much code has already been written that can
  greatly help you.
• Two types of outside code
• Modules loose collection of methods
• Classes tightly-coupled, coherent collection of
  data and methods

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Modules

• Modules are a collection of Python methods
• You can access modules by using import

import math print math.pi --- 3.14159265358
OR from math import
print pi --- 3.14159265358
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Classes

• Python is an Object-Oriented language
• Class a collection of data and methods
• Data - things
• Methods - actions

class MyClass def DoSomething() def
printSomething()
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Inheritance

• Code can inherit from classes
• myTool inherits from class SmartScript
• myTool has access to the data and methods in
  SmartScript
• To access data or methods in any class use

myTool(SmartScript.SmartScript)
self.
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Where to use self.

• When calling method
• When accessing data
• When defining a new function

self.method()
a self.dataVariable
def myNewMethod(self, arg1, arg2)
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Good Programming Practices

• Modularization
• Break up code into smaller pieces each of which
  performs some small task
• avoids long methods
• improves readability
• easier to understand/maintain
• easier to find bugs

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Good Programming Practices

• Documentation
• Should be short
• Include one sentence for each method
• In-line documentation where necessary
• Choose names well
• For methods use verbs
• For data variables use nouns

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Troubleshooting

• Use print statements
• Add code incrementally test