【coursera 学习笔记】An Introduction to Interactive Programming in Python--week0

上课地址：https://class.coursera.org/interactivepython-005/wiki/coursestaff

时间：2014.09

简介：coursera 的课，ps 在学德语中，Python德文指大蟒蛇，难怪他的图标……

平台：http://www.codeskulptor.org/viz/index.html （rice uni 的老师自己搭建的）

Syllabus

Week	Topics	Mini-project
0	Expressions, variables and assignments	"We want... a shrubbery!"
1	Functions, logic, conditionals	"Rock-Paper-Scissors-Lizard-Spock" game
2	Event-driven programming, local and global variables, buttons and input fields	"Guess the Number" game
3	The canvas, static drawing, timers, interactive drawing	Stopwatch: The Game
4	Lists, keyboard input, motion, positional/velocity control	"Pong" game
5	Mouse input, more lists, dictionaries, images	"Memory" game
6	Classes, tiled images	"Blackjack" game
7	Acceleration and friction, spaceship class, sprite class, sound	Spaceship from "RiceRocks" game
8	Sets, groups of sprites, collisions, sprite animation	Full "RiceRocks" game

concepts:

Week zeroHelp

Comments — CodeSkulptor

Non-computational parts of the program that textually describe the behavior of the program.
Comments begin with

#

, everything to right
of the hash is ignored by Python.
Comments should be frequent so you and others can understand the code.
Lecture examples - CodeSkulptor
More examples - Comments,
Strings, and Print

Strings — CodeSkulptor

Sequence of characters enclosed by a pair of single or double quotes
Examples are

"cats hate dogs"

and

'Strings
 are fun!'

.
Strings are one kind of data in Python. Their data type is denoted

str

.
Lecture examples - Hello World
More examples - Comments, Strings, and Print

# Comments, strings and print

#	Number sign(#)后面的语句都是注释.

# A string is a collection of characters enclosed by quotation
#	marks （引号）or apostrophes（撇号）

"This is a string"
'This is also a string'

# To print these strings and other things to the box on the
#	right, the word print is used.

print "Output Number One"
print 'Output Number Two'

# print statements on their own can be used to print blank（打印空白行）
#	lines to the screen, which separates output and makes it
#	easier to read. 

print
print "Hello"
print

# Multiple strings can be printed on the same line by using
#	commas to separate them.（多个输出时 用逗号隔开） This automatically inserts a 
#	space in between the two strings.（这样字符串之间会自动生成一个空格）

print "One", "Two"
print "One", "Two", "Three"
print

# If you want to include a quotation mark or apostrophe in
#	your string, you need to make the symbols around the 
#	string be the opposite type.（如果有双重引用，要用不同的号）

print "You're awesome!"
print '"Thank you!" I replied.'

# Congratulations!!! You are off to a great start :)

Numbers — Arithmetic Expressions

There are two kinds of numerical data in Python: integers and decimal numbers.
Integers correspond to the data type

int

.
Decimal numbers are represented by floating-point numbers corresponding to the data type

float

.
Floating-point numbers have around 15 decimal digits of accuracy.
In CodeSkulptor, all numbers (even integers) are represented internally as floating-point numbers.
Lecture examples - Arithmetic
Expressions
More examples - Floats
and Ints

Arithmetic Operators — Arithmetic Expressions

Five basic arithmetic operators; addition (

+

),
subtraction (

-

), multiplication (

*

),
division (

/

) and exponentiation (

**

)
CodeSkulptor implements a subset of Python 2. In Python 2, the division operator (

/

)
returns a float approximation to the exact answer if either of the operands is a float. If both operands are integers, division returns the exact answer round down to the nearest integer.
The integer division operator

//

returns
the quotient of two numbers..
Lecture examples - Arithmetic
Expressions
More examples - Arithmetic
Operations, Division

Arithmetic Expressions — Arithmetic Expressions

An arithmetic expression is either a number or an operator applied to two arithmetic expressions.
Arithmetic expressions are entered as a sequence of numbers and arithmetic operators.
Expressions are formed by grouping operators and operands via precedence: "Please excuse my dear Aunt Sallie"; parentheses, exponentiation, multiplication, division, addition, subtraction.
Lecture examples - Arithmetic Expressions
More examples - Order
of Operations for Arithmetic Expressions, Possible
Errors for Arithmetic Expressions

Variables — Variables

Variable names consist of a
sequence of letters, number and underscores (

_

).
Variable names start with a letter or underscore and are case sensitive.#以字母或者下划线打头。区分大小写
Single equals (

=

) is used for assignment
to variables. Double equals (

==

) is used for testing
equality.
Lecture examples - Variables
More examples - Variable Naming, Vabiable
Assignment, Variable
Operations, Formulas

# Arithmetic expressions - numbers, operators, expressions

print 3, -1, 3.14159, -2.8

# numbers - two types, an integer or a decimal number
# two corresponding data types int() and float()

print type(3), type(3.14159)#查看函数类型
print type(3.0)

# we can convert between data types using int() and float()
# note that int() takes the "whole" part of a decimal number and doesn't round
# float() applied to integers is boring。int（）截取浮点数的整数部分，不取舍

print int(3.14159), int(-2.8)
print float(3), float(-1)

# floating point number have around 15 decimal digits of accuracy
# pi is 3.1415926535897932384626433832795028841971...
# square root of two is 1.4142135623730950488016887242096980785696...

# approximation of pi, Python displays 12 decimal digits Python只显示12位

print 3.1415926535897932384626433832795028841971

# appoximation of square root of two, Python displays 12 decimal digits

print 1.4142135623730950488016887242096980785696

# arithmetic operators
# +		plus		addition
# -		minus		subtraction
# *		times		multiplication
# /		divided by 	division
# **    power		exponentiation

print 1 + 2, 3 - 4, 5 * 6, 2 ** 5

# Division in Python 2
# If one operand is a decimal (float), the answer is decimal

print 1.0 / 3, 5.0 / 2.0, -7 / 3.0

# If both operands are ints, the answer is an int (rounded down)

print 1 / 3, 5 / 2, -7 / 3

# expressions - number or a binary operator applied to two expressions
# minus is also a unary operator and can be applied to a single expression

print 1 + 2 * 3, 4.0 - 5.0 / 6.0, 7 * 8 + 9 * 10

# expressions are entered as sequence of numbers and operations
# how are the number and operators grouped to form expressions?
# operator precedence - "please excuse my dear aunt sallie" = (), **, *, /, +,-

print 1 * 2 + 3 * 4
print 2 + 12

# always manually group using parentheses when in doubt

print 1 * (2 + 3) * 4
print 1 * 5 * 4

# Addition
print "Ex. 1:", 4 + 5
print "Ex. 2:", 3 + 4 + 7
print

# Subtraction
print "Ex. 3:", 5 - 2
print "Ex. 4:", 3 - 7
print

# Multiplication
print "Ex. 5:", 6 * 4
print "Ex. 6:", 2 * 3 * 5
print

# Division
print "Ex. 7:", 10 / 2
print "Ex. 8:", 5 / 3

print "--------"
# Decimals, negative numbers, and fractions can also be used

# Decimals
print "Ex. 9:", 1.5 + 2.75
print "Ex. 10:", 2.0 * 1.75
print "Ex. 11:", 5.0 / 2.0 + .5
print

# Negative numbers
print "Ex. 12:", -4 + 8
print "Ex. 13:", 6 * -5
print "Ex. 14:", 4 - -3
print "Ex. 15:", -5.0 / -.75
print

# Fractions (include parenthesis)
print "Ex. 16:", (3.0 / 4.0) + (5.0 / 4.0)
print "Ex. 17:", 5 * (1.0 / 2.0)
print "Ex. 18:", -(1.0 / 2.0) * 3
print "Ex. 19:", (3.0 / 4.0) + .75
print

</pre><pre name="code" class="python">

#字符串连接：
print  “sher”+“rry”

# 数字变成字符串
print "Joe Warren" + " is " + str(52) + " years old."