10/12/2007
1
ECS 10
10/8
Outline
±
Announcements
±
Homework 2 questions
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Boolean expressions
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If/else statements
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State variables and avoiding sys.exit(…)
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Example: Coin flipping (if time permits)
Announcements
±
Professor Amenta will be back on Friday
±
Dan Alcantara will be covering Monday and
Wednesday lectures
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Email address: [email protected]
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Slides will be on class website
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Temporary location:
http://idav.ucdavis.edu/~dfalcant/ecs10/100807.ppt
Homework 2
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Homework 2 due Wednesday at 10PM
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Don’t use sys.exit(…)
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Will explain why later today
±
Questions?
Boolean expressions
if
name ==
“”
:
Boolean expression
name =
“Anonymous”
print
“We’ll call you”
, name,
“!”
Boolean algebra
±
Named after George Boole
(1815
(18151864)
1864)
±
Main idea: you can write
down logic as mathematical
formulas, as well as in
sentences.
±
Logic as a computational
system. Python does some
of this computation!
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2
Boolean
Boolean expressions
expressions
±
Boolean
Boolean is a new data type.
is a new data type.
±
Booleans can be either True or False.
±
We now have four data types (and four kinds of
expressions):
Data type
Examples
Integer
1, 10, 53
Floating point
3.14159, 6.29
String
“Hey”, “”, “String”
Boolean
True, False
Basic Boolean expressions
Expression
Expression in English
X == Y
“X is equal to Y”
X != Y
“X is
not
equal to Y”
X < Y
“X is less than Y”
X > Y
“X is greater than Y”
X <= Y
“X is less than or equal to Y”
X >= Y
“X is greater than or equal to Y”
not ______
“Whatever the condition, it’s not True”
Boolean expressions are True if the expression in English is
True, and False otherwise.
Boolean expression examples
Boolean expression
English expression
Value
“Something” == “Something”
The string “Something” is
exactly the same as the string
“Something”.
True
3 < 5
The integer 3 is less than 5.
True
3 > 5
The integer 3 is greater than 5.
False
“C
at” == “
at” == “c
at”
The string “Cat” is exactly the
same as the string “cat”.
False
“Cat” != “cat”
The string “Cat” is different
from the string “cat”.
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 Fall '07
 Amenta
 Boolean Algebra, Expression, Coin flipping

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