CPSC 231 - T09 Introduction to Computer Science
Afshin Esmaeili (2009) - CPSC 231 - T09
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Afshin Esmaeili Email:
[email protected] Office: ICT 716 (AI Lab) OR ICT 716A (Bioinformatics Lab) CT Hours: Monday 14:00 - 16:00
Afshin Esmaeili (2009) - CPSC 231 - T09
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Last Tutorial Vi and Unix commands Remotely login to lab machines Editing your Python program Shell mode vs. Script mode Type Checking Brief intro to Quickdraw Afshin Esmaeili (2009) - CPSC 231 - T09
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QuickDraw Quickdraw is a language-independent graphics API (Application Programing Interface)
It is designed to help students and beginner programmers create complex user interfaces with ease. Afshin Esmaeili (2009) - CPSC 231 - T09
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QuickDraw 1. Download QuickDraw http://pages.cpsc.ucalgary.ca/QuickDraw/index.html
Note: In windows it will be saved as quickdraw.zip 2. Rename it back to quickdraw.jar 3. In a terminal type: java -jar quickdraw.jar Note: Jar stands for Java Archive Afshin Esmaeili (2009) - CPSC 231 - T09
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Programmatically Controlling Quickdraw with Python
Output from Python program is ‘piped’ to quickdraw program. Connect your Python code to Quickdraw: python myprog.py | java -jar quickdraw.jar
Afshin Esmaeili (2009) - CPSC 231 - T09
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Lets run Quickdraw Blank window: $ java -jar quickdraw.jar
You have to make sure that quickdraw.jar is located in your current directory before running the above command. You also need to have java already installed.
Afshin Esmaeili (2009) - CPSC 231 - T09
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Lets run Quickdraw Color Selection RGB color system
The amount or intensity of each color component (red, green and blue) must be a value between 0 and 255. Python Example: print “color 0 100 255” Afshin Esmaeili (2009) - CPSC 231 - T09
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Coloring a Pixel
print “color 255 0 0” print “pixel 400 300” Afshin Esmaeili (2009) - CPSC 231 - T09
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Drawing Shapes
print “color 0 200 0” print “ellipse 400 300 200 100” Afshin Esmaeili (2009) - CPSC 231 - T09
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Variables Assignment Statement >>> message = “What’s up, Doc?” >>> n = 17 >>> pi = 3.14159
Afshin Esmaeili (2009) - CPSC 231 - T09
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Variables The assignment operator ,=, should not be confused with an equal sign. Assignment operators link a name, on the left hand side of the operator, with a value, on the right hand side. >>> 17 = n Error! Afshin Esmaeili (2009) - CPSC 231 - T09
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Variable names & keywords 1. Can be arbitrarily long 2. Can be both letters and numbers 3. Have to begin with letter 4. Case matters: Bruce and bruce are different 5. The underscore character (_) can appear in a name Afshin Esmaeili (2009) - CPSC 231 - T09
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Variable names and keywords >>> 76trombones = “big parade” SyntaxError: invalid syntax >>> more$ = 1000000 SyntaxError: invalid syntax >>> class = “Computer Science 231” SyntaxError: invalid syntax
Afshin Esmaeili (2009) - CPSC 231 - T09
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Variables Print Statement also works with variables >>> print message What’s up, Doc? >>> print n 17 >>> print pi 3.14159
Afshin Esmaeili (2009) - CPSC 231 - T09
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Variables Variables also have types >>> type(message)
>>> type(n) >>> type(pi) Afshin Esmaeili (2009) - CPSC 231 - T09
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Keywords Python has thirty-one keywords and
del
from
not
while
as
elif
global
or
with
assert
else
if
break class
except import print exec
continue finally def
pass yeild
for
in
raise
is
return
lambda
try
Keywords define the language’s rules and structure Afshin Esmaeili (2009) - CPSC 231 - T09
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Operators & Operands Operators are special symbols that represent computations 20 + 30 hour - 1 hour * 60 + minute minute / 60 5 ** 2 (5+9)*(15-7) Note: The asterisk (*) is the symbol for multiplication, and ** is the symbol for exponentiation
Afshin Esmaeili (2009) - CPSC 231 - T09
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Operators & Operands >>> minute = 59 >>> minute / 60 0 The value of minute is 59, and 59 divided by 60 is 0.98333, not 0. The reason for the discrepancy is that Python is performing integer division.
>>> minute = 59.0 >>> minute / 60 0.983333333333328 Afshin Esmaeili (2009) - CPSC 231 - T09
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Operation on strings Can not perform mathematica operations on strings “Hello”/123 message*”Hello” message-1 “15”+2
Afshin Esmaeili (2009) - CPSC 231 - T09
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Operations on strings
>>> fruit = “banana” >>> baked_good = “nut bread” >>> print fruit + baked_good
Afshin Esmaeili (2009) - CPSC 231 - T09
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Input Create a .py file with the following content: n = raw_input(“Please enter your name: “) print n n = input(“Enter a numerical expression: “) print n
Afshin Esmaeili (2009) - CPSC 231 - T09
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References
“How to Think Like a Computer Scientist, Learning with Python” - Chapter 2. http://pages.cpsc.ucalgary.ca/~zongpeng/CPSC231/lectures/ch2.pdf “Quickdraw” http://pages.cpsc.ucalgary.ca/QuickDraw/index.html
Afshin Esmaeili (2009) - CPSC 231 - T09
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