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# 第3章 最初的步骤
print("What's your name?") #Python是大小写敏感的Python是大小写敏感的 确保在每一行的开始字符前没有空格或者制表符
help(str)
quit()
copyright()
credits()
license()
help('print')

# 第4章 基本概念
"This is the first sentence.\
This is the second sentence."
# 行末的单独一个反斜杠表示字符串在下一行继续，而不是开始一个新的行

# 标识符的命名
开头字母或_
标识符区分大小写
标识符其他部分可以由字母/下划线/数字组成

# 例4.1 使用变量和字面意义上的常量
i=5
print(i)
i=i+1
print(i)

s = '''This is a multi-line string.
This is the second line.'''
print(s)

# 逻辑行与物理行 ps:在每个物理行只写一句逻辑行,避免使用分号
i=5;
print(i);

i=5;print(i);
i=5;print(i)

# 用单引号括起来换行要加"\",用三引号则可不加
s = 'This is a string. \
This continues the string.'
print(s)

# 第5章 运算符与表达式
2 + 3
'a'+'b'
8//3  #取整除,返回商的整数部分
5%3 #取模
2<<2 #得8,左移,低位补零,二进制
11>>1 #得5,右移,高位丢弃(丢弃最右边一位),二进制

& 	按位与 	数的按位与 	5 & 3得到1。
| 	按位或 	数的按位或 	5 | 3得到7。
^ 	按位异或 	数的按位异或 	5 ^ 3得到6
~ 	按位翻转 	x的按位翻转是-(x+1) 	~5得到6。

3<5<7

# 第6章 控制流
# if-elif-else
number=23
guess=int(input('Enter an integer : '))
if guess==number:
    print("Congratulations, you guessed it.")
    print("(but you do not win any prizes!)")
elif guess<number:
    print("No, it is a little higher than that")
else:
    print("No, it is a little lower than that")
print("done")

# while-else
number=23
running=True  #这里running要设为True或者1才有效
while running:
    guess=int(input("Enter an integer : "))
    if guess==number:
        print("Congratulations, you guessed it.")
        running=False  #改成break有同样的效果
    elif guess<number:
        print("No, it is a little higher than that")
    else:
        print("No, it is a little lower than that")
else:
    print("The while loop is over.")
print("Done")

# for..in
for i in range(1,5,2):  #注意这里以冒号结尾,[1,5),步长为2
    print(i)
else:
    print("over")

# break
while True:
    s=input('Enter something : ')
    if s == 'quit':
        break
    print('Length of the string is',len(s))
print('done')

# continue
while True:
    s=input('Enter something : ')
    if s=='quit':
        break
    if len(s)<3:
        continue #忽略块中的剩余的语句
    print('Input is of sufficient length')

# 第7章 函数
# 定义函数
def sayhello():
    print('hello')
sayhello()

# 使用函数形参
def printMax(a,b):
    if a>b:
        print(a,'is maximum')
    else:
        print(b,'is maximum')
printMax(3,4)
x=5
y=7
printMax(x,y)

# 使用局部变量 x的值在函数里改变了,但实际x的值在全局里没有改变
def func(x):
    print('x is',x)
    x=2
    print('Changed local x to',x)

x=50
func(x)
print('x is still',x)

# 使用Global语句 此时全局变量x会改变
def func():
    global x
    print('x is',x)
    x=2
    print('Changed local x to',x)

x=50
func()
print('Value of x is',x)

# 使用默认参数值
def say(message,times=1):
    print(message*times)
say('Hello')
say('World ',5)

#重要只有在形参表末尾的那些参数可以有默认参数值，即你不能在声明函数形参的时候，先声明有默认值的形参而后声明没有默认值的形参。
#这是因为赋给形参的值是根据位置而赋值的。例如，def func(a, b=5)是有效的，但是def func(a=5, b)是 无效 的。

# 使用关键参数
def func(a,b=5,c=10):
    print('a is',a,'b is',b,'c is',c)
func(3,7)
func(25,c=24)
func(c=50,a=100)

# return语句
def maximum(x,y):
    if x>y:
        return x
    else:
        return y

print(maximum(2,3))

def someFunction():
    pass
print(someFunction()) #return None

# 使用DocStrings-文档字符串
def printMax(x,y):
    '''Prints the maximum of two numbers.

        The two values must be integers.'''
    x=int(x)
    y=int(y)
    if x>y:
        print(x,'is maximum')
    else:
        print(y,'is maximum')
printMax(3,5)
print(printMax.__doc__)
# 文档字符串的惯例是一个多行字符串，它的首行以大写字母开始，句号结尾。第二行是空行，从第三行开始是详细的描述。

help(printMax) #原理就是抓取函数的__doc__属性

# 第8章 模块
import sys

print ('The command line arguments are:')
for i in sys.argv:
    print (i)
print ('\n\nThe PYTHONPATH is', sys.path, '\n')

# 使用模块的__name__
if __name__ == '__main__':
    print('This program is being run by itself')
else:
    print('I am being imported from another module')

def sayhi():
    print('Hi, this is mymodule speaking.')

version = '0.1'

import mymodule

mymodule.sayhi()
print('Version', mymodule.version)

from mymodule import sayhi, version
sayhi()
print('Version', version)

# dir()函数 列出模块定义的标识符。标识符有函数、类和变量
import mymodule
dir(mymodule)
a=5
dir()
del a
dir()

# 第9章 数据结构
# 使用列表
shoplist=['apple','mango','carrot','banana']
print('I have',len(shoplist),'item to purchase')
print('These items are:',end=' ')
for item in shoplist:
    print(item,end=' ')
print('\nI also have to buy rice.')
shoplist.append('rice')
print('My shopping list is now',shoplist)
print('I will sort my list now')
shoplist.sort()
print('The first item I will buy is',shoplist[0])
olditem=shoplist[0]
del shoplist[0]
print('I bought the',olditem)
print('My shopping list is now',shoplist)

# 使用元组 元组和字符串一样是 不可变的 即你不能修改元组
zoo=('wolf','elephant','penguin')
print('Number of animals in the zoo is',len(zoo))
new_zoo=('monkey','dolphin',zoo)
print('Number of animals in the new zoo is',len(new_zoo)) #还是3,这里zoo被当成一个单位
print('All animals in new zoo are', new_zoo)
print('Animals brought from old zoo are', new_zoo[2])
print('Last animal brought from old zoo is', new_zoo[2][2])

singleton = (2 , )

# 元组与打印语句
age=22
name='Swaroop'
print('%s is %d years old' %(name,age)) #%s表示字符串,%d表示整数
# print的这个用法使得编写输出变得极其简单，它避免了许多字符串操作。它也避免了我们一直以来使用的逗号。
print('Why is %s playing with that python?' %name)

# 字典
ab = {       'Swaroop'   : 'swaroopch@byteofpython.info',
             'Larry'     : 'larry@wall.org',
             'Matsumoto' : 'matz@ruby-lang.org',
             'Spammer'   : 'spammer@hotmail.com'
     }
print("Swaroop's address is %s" %ab['Swaroop'])

# Adding a key/value pair
ab['Guido']='guido@python.org'
# Deleting a key/value pair
del ab['Spammer']
print('\nThere are %d contacts in the address-book\n' %len(ab))
for name,address in ab.items():
    print('Contact %s at %s' %(name,address))

# 序列
shoplist=['apple','mango','carrot','banana']

# Slicing on a list
print('Item 0 is',shoplist[0])
print('Item -1 is',shoplist[-1]) #右数第一个
shoplist[1:3] #['mango', 'carrot'] 不包括最右边的对象,即[1,3)
print('Item 2 to end is', shoplist[2:])
print('Item start to end is', shoplist[:])

# Slicing on a string
name='swaroop'
print('characters 1 to 3 is',name[1:3])

# 对象和参考
print('Simple Assignment')
shoplist=['apple','mango','carrot','banana']
mylist=shoplist # mylist is just another name pointing to the same object!
del shoplist[0]
print('shoplist is',shoplist)
print('mylist is',mylist)
# 小结:如果是要获得一份拷贝,则使用mylist=shoplist[:],如果是想使用另一个变量名参考同一个对象,则使用mylist=shoplist

# 更多字符串的内容
name='Swaroop'
if name.startswith('Swa'):
    print('Yes, the string starts with "Swa"')
if 'a' in name:
    print('Yes, it contains the string "a"')
if name.find('war')!=-1: #这里存在是1,不存在是-1
    print('Yes, it contains the string "war"')
delimiter = '_*_'
mylist = ['Brazil', 'Russia', 'India', 'China']
print(delimiter.join(mylist))

# 第10章 解决问题——编写一个Python脚本(略)

# 第11章 面向对象的编程
# 类
class Person:
    pass
p=Person()
print(p) #计算机内存地址

# 使用对象的方法
class Person:
    def sayHi(self):
        print('Hello')
p=Person()
p.sayHi()
Person().sayHi()

# __init__方法 在类的一个对象被建立时，马上运行。这个方法可以用来对你的对象做一些你希望的初始化
class Person:
    def __init__(self,name):
        self.name=name
    def sayHi(self):
        print("Hello,my name is",self.name)
p=Person('Swaroop')
p.sayHi()

#类的变量 由一个类的所有对象（实例）共享使用。只有一个类变量的拷贝，所以当某个对象对类的变量做了改动的时候，这个改动会反映到所有其他的实例上。
#对象的变量 由类的每个对象/实例拥有。因此每个对象有自己对这个域的一份拷贝，即它们不是共享的，在同一个类的不同实例中，虽然对象的变量有相同的名称，但是是互不相关的。

class Person:
    population=0 #类的变量
    def __init__(self,name):
        self.name=name #对象的变量
        print('Initializing %s' %self.name)
        Person.population+=1 #Person.population=Person.population+1
    def __del__(self):
        print('%s says bye' %self.name)
        Person.population-=1

        if Person.population==0:
            print('I am the last one.')
        else:
            print('There are still %d people left.' %Person.population)
    def sayHi(self):
        print('Hi,my name is %s.' %self.name)
    def howMany(self):
        if Person.population==1:
            print('I am the only person here.')
        else:
            print('We have %d persons here.' %Person.population)
swaroop = Person('Swaroop')
swaroop.sayHi()
swaroop.howMany()

kalam = Person('Abdul Kalam')
kalam.sayHi()
kalam.howMany()

swaroop.sayHi()
swaroop.howMany()

# 继承
class SchoolMember:
    '''Represents any school member.'''
    def __init__(self, name, age):
        self.name = name
        self.age = age
        print('(Initialized SchoolMember: %s)' % self.name)

    def tell(self):
        '''Tell my details.'''
        print('Name:"%s" Age:"%s"' % (self.name, self.age))

class Teacher(SchoolMember):
    '''Represents a teacher.'''
    def __init__(self, name, age, salary):
        SchoolMember.__init__(self, name, age)
        self.salary = salary
        print('(Initialized Teacher: %s)' % self.name)

    def tell(self):
        SchoolMember.tell(self)
        print('Salary: "%d"' % self.salary)

class Student(SchoolMember):
    '''Represents a student.'''
    def __init__(self, name, age, marks):
        SchoolMember.__init__(self, name, age)
        self.marks = marks
        print('(Initialized Student: %s)' % self.name)

    def tell(self):
        SchoolMember.tell(self)
        print('Marks: "%d"' % self.marks)

t = Teacher('Mrs. Shrividya', 40, 30000)
s = Student('Swaroop', 22, 75)

print()# prints a blank line

members = [t, s]
for member in members:
    member.tell() # works for both Teachers and Students

# 第12章 输入/输出
# 使用文件
poem='''\
Programming is fun
When the work is done
if you wanna make your work also fun:
        use Python!
'''

f=open('poem.txt','w') # open for 'w'riting
f.write(poem)
f.close()

f=open('poem.txt') # if no mode is specified, 'r'ead mode is assumed by default
while True:
    line=f.readline()
    if len(line)==0:
        break
    print(line,end=' ')
f.close()

# 储存器
import pickle as p
shoplistfile='shoplist.data'
shoplist=['apple','mango','carrot']
f=open(shoplistfile,'wb')
p.dump(shoplist,f) #将对象shoplist保存到f中去
f.close()
# 在python3以上版本中，如果要用存储器，那么读写文件都要用‘rb’和'wb'模式。
del shoplist #remove the shoplist
#Read back from the storage
f=open(shoplistfile, "rb")
storedlist=p.load(f)
print(storedlist)

# 第13章 异常
# 处理异常
import sys
try:
    s=Input('Enter something --> ')
except NameError:
    print('Why did you do an EOF on me' )
    sys.exit()
except:
    print('Some error/exception occurred')

print('Done')

# 第15章 更多Python的内容
# 使用列表综合
listone=[2,3,4]
listtwo=[2*i for i in listone if i > 2]
print(listtwo)

# 在函数中接收元组和列表
def powersum(power,*args): #args是用来存储多余的参数
    total=0
    for i in args:
        total+=pow(i,power) #i的power次方
    return total
powersum(2,3,4) #3的平方加4的平方
powersum(2,10)

# lambda形式 用来创建新的函数对象，并且在运行时返回它们
def make_repeater(n):
    return lambda s:s*n

twice=make_repeater(2)

print(twice('word'))
print(twice(5))

# assert语句 用来声明某个条件是真的
mylist=['item']
assert len(mylist)>=1
mylist.pop(-1) #移除最右一个对象
assert len(mylist)>=1

# repr函数 用来取得对象的规范字符串表示
i=[]
i.append('item')
i
repr(i)