Lesson 2 - Fundamentals of programming languages - University of ...

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Nov 7, 2013 (3 years and 7 months ago)

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Python Mini
-
Course

University of Oklahoma

Department of Psychology

Day 1


Lesson 2

Fundamentals of Programming
Languages

4/5/09

Python Mini
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Course: Day 1
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Lesson 2

1

Lesson objectives

1.
Describe the basic structure of the
Python language

2.
Use the IDLE interactive
interpreter

3.
Identify three kinds of errors that
occur in programming and
describe how to correct them

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Course: Day 1
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Lesson 2

2

Formal languages


Designed for specific apps


Ex: mathematical notation


Have strict rules for syntax



3 + 3 = 6



3+ = 3$6
(bad syntax)


Are literal and unambiguous


Structure is critical

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3

Programming languages


Formal languages that are
designed to express computations
and algorithms


Low level


One step removed from the 1’s and 0’s
used by the computer


High level


More human
-
friendly languages

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4

Translating


High level language must be
translated into low level language
by either:


Interpreter (at run
-
time)


Compiler (creates a file containing
executable object code)


Python is an interpreted language

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Lesson 2

5

Starting IDLE


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Programs


Programs are sequences of
instructions


Input


Output


Math and data manipulation


Conditional execution


Repetition

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Lesson 2

7

The “Hello, World” program


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Scripts


A script is a file that contains a
program in a high
-
level
language for an interpreter


Python scripts are text files
ending in .py


Create HelloWorld.py

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Executing scripts


Python scripts are run in a
“shell”


This can be IDLE, a terminal shell
(OS X, Linux, Unix), or a
command prompt window (MS
Windows)


Run HelloWorld.py in IDLE

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Course: Day 1
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10

Debugging


You will make mistakes while
programming!


These mistakes are called
“bugs” and the process of
tracking them down and
eliminating them is debugging

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Course: Day 1
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11

Syntax Errors


All programming languages are
picky about syntax


Try this:


1 + 2) + 3


Syntax errors can be identified
using automated code checking
(color coding) and by error
messages

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Course: Day 1
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12

Runtime errors


Errors that occur when
program is running


Also called “exceptions”


Ex: runtime.py


Identified by testing the
program (this includes using
test modules)

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Course: Day 1
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Semantic or logical error


Program runs (and does
exactly what you told it to do)


But you made a mistake in the
design or implementation


Identified by case
-
based
testing

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Course: Day 1
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