python入门 -- 学习笔记1

学习资料：笨方法学Python

准备：

• 安装环境----请自行网络搜索（Windows安装很简单，和其他安装程序一样）
• 找一个自己习惯的编辑器（比如：sublime text 3）
• 创建一个专门的目录，按着资料把所有的代码敲一遍  --  可了解下DOS基本命令

1、第一个程序

　　文件命名方式： 文件.py

　　执行方式：python 文件.py （在该文件路径下执行）

　　若执行错误，会有报错提示，看不懂可以从搜索引擎中查询

　　字符串的表示有几种方式，你注意到了吗~，还可以继续搜索是否有其他表示方式

正确代码及结果：

　　

错误代码及结果：可以根据提示进行搜索错误原因，并可通过提示查找对应的错误代码行进行检查

　　

　　

习题2：注释与井号----程序里的注释是很重要的

代码：

# A comment,this is so you can read your program later.

# Anything after the # is ingnored by python.

print "I could have code like this." # and the comment after is ignored

# You can also use a comment to "disable" or comment out a piece of code:
# print "This won't run."

print "This will run"

运行：

　　

习题3：数字和数学计算

• + plus  加法计算
• - minus  减法计算
• / slash  除法计算（保留商，舍弃余数）
• * asterisk 乘法计算
• % percent 模计算（取余数）
• < less-than 比较运算  小于号 
• > greater-than 比较运算  大于号
• <= less-than-equal 比较运算  小于等于号
• >= greater-than-equal 比较运算  大于等于号

代码：建议养成良好的代码习惯，加空格

print "I will count my chickens:"

print "Hens", 25 + 30 / 6
print "Roosters", 100 - 25 * 3 % 4

print "Now I will count the eggs:"

print 3 + 2 + 1 - 5 + 4 % 2 - 1 /4 + 6

print "Is it true that 3 + 2 < 5 - 7?"

print 3 + 2 < 5 - 7

print "What is 3 + 2?", 3 + 2
print "What is 5 - 7?", 5 - 7

print "Oh, that's why it's False."

print "How about some more."

print "Is it greater?", 5 > -2
print "Is it greater or egual?", 5 >= -2
print "Is it less or egual?", 5 <= -2

结果：

　　

习题4：变量和命名 -- 某东西的名字，在程序中建议以变量代表的真实含义用英语命名，亦可多个单词以“_”拼接

命名规范：适用字母、数字、下划线，数字不能开头

备注：字符串与变量的区别？   变量不用引号，直接调用变量名

代码：

cars = 100
space_in_a_car = 4.0
drivers = 30
passengers = 90
cars_not_driven = cars - drivers
cars_driven = drivers 
carpool_capacity = cars_driven * space_in_a_car
average_passengers_per_car = passengers / cars_driven

print "There are", cars, "cars available."
print "There are only", drivers, "drivers available."
print "There will be", cars_not_driven, "empty cars today."
print "We van transport", carpool_capacity, "people today."
print "We have", passengers, "to carpool today."
print "We need to put about", average_passengers_per_car, "in each car."

结果：

　　

习题5：更多的变量及打印

　　字符串是程序将信息展示给人的方式。可以打印它们，可以将它们写入文件，还可以将它们发送给网站服务器，很多事情都是通过字符串交流实现。本习题引入格式化字符串。

常用：%s  字符串   ；  %d  整数  ； %f   浮点数  ； %r  自然字符串  ，其余可搜索看看，另可查查%s和%r有什么不同~（  和 print "%r" % "\n"）

格式："%s"   %  对应的变量（变量多个时，用圆括号括起来，与前面一一对应，中间用逗号隔开）

注意：大小写敏感，my_age和My_age代表不同的变量

　　　如果使用了非ASCII字符碰到了编码错误，记得在最顶端加一行   # coding: utf-8

代码：

my_name = 'Zed A. Shaw'

my_age = 35
my_height = 74
my_weight = 180 
my_eyes = 'Brown'
my_teeth = 'White'
my_hair = 'Black'

print "Let's talk about %s." % my_name
print "He's %d inches tail." % my_height
print "He's %d pounds heavy." % my_weight
print "Actually that's not too heavy."
print "He's got %s eyes and %s hair." % (my_eyes, my_hair)
print "His teeth are usually %s depending on the coffee." % my_teeth

# this line is trick, try to get it exactly right
print "If I add %d, %d, and %d I get %d." % (my_age, my_height, my_weight, my_age + my_height + my_weight)

结果：

习题6：字符串和文本

备注：字符串拼接可以使用“+”

--   “+” 表示拼接   “，”主要是分割参数的一种方式

代码：

X = "There are %d types of people." % 10
binary = "binary"
do_not = "don't"
Y = "those who know %s and those who %s." % (binary, do_not)

print X
print Y

print "I siad: %r." % X
print "I also said: '%s'." % Y

hilarious = False
joke_evaluation = "Isn't that joke so funny?! %r"

print joke_evaluation % hilarious

w = "This is the left side of..."
e = "a string with a right side."

print w + e

结果：

习题7：更多打印

备注：代码倒数第二行的打印，最后的逗号注意到了吗？不加的话会有怎样的效果呢？

代码：

print "Mary had a little lamb."
print "Its fleece was white as %s." % 'snow'
print "And everywhere that Mary went."
print "." * 10 # what'd that do?

end1 = "C"
end2 = "h"
end3 = "e"
end4 = "e"
end5 = "s"
end6 = "e"
end7 = "B"
end8 = "u"
end9 = "r"
end10 = "g"
end11 = "e"
end12 = "r"

# watch that comma at the end. try removing it to see what happens
print end1 + end2 + end3 + end4 + end5 +end6,
print end7 + end8 + end9 + end10 + end11 + end12

结果：

习题8：打印，打印

代码：

formmatter = "%r %r %r %r"

print formmatter % (1, 2, 3, 4)
print formmatter % ("one", "two", "three", "four")
print formmatter % (True, False, False, True)
print formmatter % (formmatter, formmatter, formmatter, formmatter)
print formmatter % (
　　　　　　　　"I had this thind.",
　　　　　　　　"That you could type up right.",
　　　　　　　　"But it didn't sing.",
　　　　　　　　"So I said goodnight."
)

结果：

习题9：打印，打印，打印

备注：代码中三个连着的双引号有什么作用？使用三个连着的单引号可以吗？\n 的作用？

　　　--    """ 多行

　　　　　　文本

　　　　　"""

　　　--  \n   转义字符，表示新起一行      是否还有其他类似的转义字符？

代码：

# Here's some new strange stuff, remember type it exactly.

days = "Mon Tue Wed Thu Fri Sat Sun"
months = "Jan\nFeb\nMar\nApr\nMay\nJun\nJuly\nAug"

print "Here are the days: ", days
print "Here are the months: ", months

print """
　　There's something going on here.
　　With the three double-guotes.
　　We'll be able to type as much as we like.
　　Even 4 lines if we want, or 5, or 6.
"""

结果：

习题10：那是什么？

备注：更多的转义字符 --  \t   \\  \'    \"  \r ...

　　"I "understand" joe."   --   这样表达会有什么问题？怎样解决呢？

　　--  会认为understand左侧的引号为结束引号，将报错，可通过转义字符解决   "I \"understand\" joe."

代码：

tabby_cat = "\tI'm tabbed in."
persian_cat = "I'm split\non a line."
backslash_cat = "I'm \\ a \\ cat."

fat_cat = """
　　I'll do a list:
　　\t* Cat food
　　\t* Fishies
　　\t* Catnip\n\t* Grass
"""

print tabby_cat
print persian_cat
print backslash_cat
print fat_cat

结果：