当我们编写Python代码时，我们得到的是一个包含Python代码的以.py为扩展名的文本文件。要运行代码，就需要Python解释器去执行.py文件

在写代码之前，请千万不要用“复制”-“粘贴”把代码从页面粘贴到你自己的电脑上。写程序也讲究一个感觉，你需要一个字母一个字母地把代码自己敲进去，在敲代码的过程中，初学者经常会敲错代码，所以，你需要仔细地检查、对照，才能以最快的速度掌握如何写程序。

输出

字符串：
print(“hello, world”) 则输出hello, world
等价于print(‘hello, world’)。
双引号和单引号在这里是一样的。

多个字符串：

print(“hello word”, “i love you”, ‘or you’)
遇到逗号的时候会自动输出一个空格

name = input(‘please enter your name: ‘)

print(‘hello,’, name)

先输出please enter your name

然后等待从键盘上输入name，最后再输出hello, name的值

#开头的是注释

以冒号结尾的表明这是个代码块

对于浮点数用e代表10

and是与运算 or是或运算 not是非运算

空值是None 不是0 0有意义，None是一个特殊的值

//python中称为地板除，省略小数，向下取整

print(10 // 3)

> 3

s3 = 'i can "love" you'
print(s3)

> i can "love" you

外面用双引号里边的单引号不用转义字符，同理外面用单引号，里面的双引号也不用转义字符。

s1 = 'hello\nworld'
print(s1)

> hello
  world

\n相当于回车

s1 = r'hello\nworld'
print(s1)
hello\nworld
>

前面有r将引号中的内容输出来，内部字符串默认不转义。

s2 = “hello,\

world”等价于s2 = “hello, world” 当要写成两行的时候则要用一个\来连接上下行

s3 = ”’hello,

world,

hahaha”’

等价于

s3 = ‘hello,\nworld,\nhahaha’

外面用双引号里边的单引号不用转义字符

s3 = ‘i can “love” you’

在计算机内存中，统一使用Unicode编码，当需要保存到硬盘或者需要传输的时候，就转换为UTF-8编码。

words = 'for you ' * 3

print(words)

> for you for you for you

name = ‘My Name is Mike’

print(name[0]) R：M

print(name[-4])从后面数第四个 R：M

print(name[11:14]) R：Mik

print(name[11:15]) R: Mike

print(name[5:]) R：me is Mike

print(name[: 5]) R：My Na

[x , y]从x起到y，不包括y

注意的一点是从0开始数的，不是从1

phone_number = '13866660006'

hiding_number = phone_number.replace(phone_number[3:7],'*' * 4)

print(hiding_number)

R：138****0006

replace进行遮挡第一个表示要被遮挡的内容，后面的表示用什么遮挡 

search = '168'

num_a = '1386-168-0006'

num_b = '1681-789-0006'

print(search + ' is at ' + str(num_a.find(search)) + ' to ' + str(num_a.find(search) +  len(search)) + ' of num_a ')

print(search + ' is at ' + str(num_b.find(search)) + ' to ' + str(num_b.find(search) + len(search)) + ' of num_b ')

R：
168 is at 5 to 8 of num_a

168 is at 0 to 3 of num_b 

print('{} a word she can get what she {} for.'.format('With','came'))

print('{preposition} a word she can get what she {verb} for'.format(preposition = 'With', verb = 'came'))

print('{0} a word she can get what she {1} for.'.format('With','came'))

R：
With a word she can get what she came for.

With a word she can get what she came for

With a word she can get what she came for.

desktop_path = 'D:\Desktop'//桌面的路径
    full_path = desktop_path + '/'+name + '.txt'
    file = open(full_path,'w')//打开此路径，没有则创建一个
    file.write(msg)//将msg的内容写到路径中
    file.close()//关闭文件
text_create('hello','hello world i')
str = "this is string example....wow!!! this is really string"
print (str.replace("is", "was"))
print (str.replace("is", "was", 2))

R:
thwas was string example….wow!!! thwas was really string

thwas was string example….wow!!! this is really string

将str中的is全部用was代替

str中的is被was代替两次

def text_filter(word,censored_word = 'lame',changed_word = 'Awesome'):#替换过滤字
    return word.replace(censored_word,changed_word)
def text_cencored_create(name,msg):
    cleanmsg = text_filter(msg)
    desktop_path = 'D:\Desktop'
    full_path = desktop_path + '/' + name + '.txt'
    file = open(full_path,'w')
    file.write(cleanmsg)
    file.close()
text_cencored_create('Try','lame!lame!lame!lame')