Python基础----函数

1、作用域：

对于变量的作用域，执行声明并在内存中存在，该变量就可以在下面的代码中使用。

if 1==1:
    name = 'wupeiqi'
print  name

下面的结论对吗？

外层变量，可以被内层变量使用

内层变量，无法被外层变量使用

2、三元运算

三元运算（三目运算），是对简单的条件语句的缩写。

# 书写格式
 
result = 值1 if 条件 else 值2
 
# 如果条件成立，那么将 “值1” 赋值给result变量，否则，将“值2”赋值给result变量
基本数据类型补充

3、二进制：

4、基本数据类型补充

set：set集合，是一个无序且不重复的元素集合

class set(object):
    """
    set() -> new empty set object
    set(iterable) -> new set object
     
    Build an unordered collection of unique elements.
    """
    def add(self, *args, **kwargs): # real signature unknown
        """
        Add an element to a set，添加元素
         
        This has no effect if the element is already present.
        """
        pass
 
    def clear(self, *args, **kwargs): # real signature unknown
        """ Remove all elements from this set. 清除内容"""
        pass
 
    def copy(self, *args, **kwargs): # real signature unknown
        """ Return a shallow copy of a set. 浅拷贝  """
        pass
 
    def difference(self, *args, **kwargs): # real signature unknown
        """
        Return the difference of two or more sets as a new set. A中存在，B中不存在
         
        (i.e. all elements that are in this set but not the others.)
        """
        pass
 
    def difference_update(self, *args, **kwargs): # real signature unknown
        """ Remove all elements of another set from this set.  从当前集合中删除和B中相同的元素"""
        pass
 
    def discard(self, *args, **kwargs): # real signature unknown
        """
        Remove an element from a set if it is a member.
         
        If the element is not a member, do nothing. 移除指定元素，不存在不保错
        """
        pass
 
    def intersection(self, *args, **kwargs): # real signature unknown
        """
        Return the intersection of two sets as a new set. 交集
         
        (i.e. all elements that are in both sets.)
        """
        pass
 
    def intersection_update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the intersection of itself and another.  取交集并更更新到A中 """
        pass
 
    def isdisjoint(self, *args, **kwargs): # real signature unknown
        """ Return True if two sets have a null intersection.  如果没有交集，返回True，否则返回False"""
        pass
 
    def issubset(self, *args, **kwargs): # real signature unknown
        """ Report whether another set contains this set.  是否是子序列"""
        pass
 
    def issuperset(self, *args, **kwargs): # real signature unknown
        """ Report whether this set contains another set. 是否是父序列"""
        pass
 
    def pop(self, *args, **kwargs): # real signature unknown
        """
        Remove and return an arbitrary set element.
        Raises KeyError if the set is empty. 移除元素
        """
        pass
 
    def remove(self, *args, **kwargs): # real signature unknown
        """
        Remove an element from a set; it must be a member.
         
        If the element is not a member, raise a KeyError. 移除指定元素，不存在保错
        """
        pass
 
    def symmetric_difference(self, *args, **kwargs): # real signature unknown
        """
        Return the symmetric difference of two sets as a new set.  对称差集
         
        (i.e. all elements that are in exactly one of the sets.)
        """
        pass
 
    def symmetric_difference_update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the symmetric difference of itself and another. 对称差集，并更新到a中 """
        pass
 
    def union(self, *args, **kwargs): # real signature unknown
        """
        Return the union of sets as a new set.  并集
         
        (i.e. all elements that are in either set.)
        """
        pass
 
    def update(self, *args, **kwargs): # real signature unknown
        """ Update a set with the union of itself and others. 更新 """
        pass

练习：寻找差异

# 数据库中原有
old_dict = {
    "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 },
    "#2":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
    "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
}
   
# cmdb 新汇报的数据
new_dict = {
    "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 800 },
    "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }
    "#4":{ 'hostname':c2, 'cpu_count': 2, 'mem_capicity': 80 }
}

练习：寻找差异

1 2 3 4 5 6 7 8 9 10 11 12 13

# 数据库中原有 old_dict = {     "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 },     "#2":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }     "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 } }     # cmdb 新汇报的数据 new_dict = {     "#1":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 800 },     "#3":{ 'hostname':c1, 'cpu_count': 2, 'mem_capicity': 80 }     "#4":{ 'hostname':c2, 'cpu_count': 2, 'mem_capicity': 80 } }

需要删除：？
需要新建：？
需要更新：？ 
注意：无需考虑内部元素是否改变，只要原来存在，新汇报也存在，就是需要更新

3、深浅拷贝

一、数字和字符串

对于 数字 和 字符串 而言，赋值、浅拷贝和深拷贝无意义，因为其永远指向同一个内存地址。

二、其他基本数据类型

对于字典、元祖、列表 而言，进行赋值、浅拷贝和深拷贝时，其内存地址的变化是不同的。

1、赋值

赋值，只是创建一个变量，该变量指向原来内存地址，如：

2、浅拷贝

浅拷贝，在内存中只额外创建第一层数据

import copy
  
n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}
  
n3 = copy.copy(n1)

3、深拷贝

深拷贝，在内存中将所有的数据重新创建一份（排除最后一层，即：python内部对字符串和数字的优化）

import copy

  

n1 = {"k1": "wu", "k2": 123, "k3": ["alex", 456]}

  

n4 = copy.deepcopy(n1)

 

函数

对于上述的两种实现方式，第二次必然比第一次的重用性和可读性要好，其实这就是函数式编程和面向过程编程的区别：

• 函数式：将某功能代码封装到函数中，日后便无需重复编写，仅调用函数即可
• 面向对象：对函数进行分类和封装，让开发“更快更好更强...”

函数式编程最重要的是增强代码的重用性和可读性

二、定义和使用

def 函数名(参数):
       
    ...
    函数体
    ...
    返回值

函数的定义主要有如下要点：

• def：表示函数的关键字
• 函数名：函数的名称，日后根据函数名调用函数
• 函数体：函数中进行一系列的逻辑计算，如：发送邮件、计算出 [11,22,38,888,2]中的最大数等...
• 参数：为函数体提供数据
• 返回值：当函数执行完毕后，可以给调用者返回数据。

1、返回值

函数是一个功能块，该功能到底执行成功与否，需要通过返回值来告知调用者。

以上要点中，比较重要有参数和返回值：

def 发送短信():
       
    发送短信的代码...
   
    if 发送成功:
        return True
    else:
        return False
   
   
while True:
       
    # 每次执行发送短信函数，都会将返回值自动赋值给result
    # 之后，可以根据result来写日志，或重发等操作
   
    result = 发送短信()
    if result == False:
        记录日志，短信发送失败...

2、参数

为什么要有参数？

def CPU报警邮件()
    #发送邮件提醒
    连接邮箱服务器
    发送邮件
    关闭连接

def 硬盘报警邮件()
    #发送邮件提醒
    连接邮箱服务器
    发送邮件
    关闭连接

def 内存报警邮件()
    #发送邮件提醒
    连接邮箱服务器
    发送邮件
    关闭连接
 
while True：
 
    if cpu利用率 > 90%:
        CPU报警邮件（）
 
    if 硬盘使用空间 > 90%:
        硬盘报警邮件（）
 
    if 内存占用 > 80%:
        内存报警邮件（）

def 发送邮件(邮件内容)

    #发送邮件提醒
    连接邮箱服务器
    发送邮件
    关闭连接

 
while True：
 
    if cpu利用率 > 90%:
        发送邮件("CPU报警了。")
 
    if 硬盘使用空间 > 90%:
        发送邮件("硬盘报警了。")
 
    if 内存占用 > 80%:
        发送邮件("内存报警了。")

函数的有三中不同的参数：

• 普通参数
• 默认参数
• 动态参数

# ######### 定义函数 ######### 

# name 叫做函数func的形式参数，简称：形参
def func(name):
    print name

# ######### 执行函数 ######### 
#  'wupeiqi' 叫做函数func的实际参数，简称：实参
func('wupeiqi')

def func(name, age = 18):
    
    print "%s:%s" %(name,age)

# 指定参数
func('wupeiqi', 19)
# 使用默认参数
func('alex')

注：默认参数需要放在参数列表最后

def func(*args):

    print args


# 执行方式一
func(11,33,4,4454,5)

# 执行方式二
li = [11,2,2,3,3,4,54]
func(*li)

def func(**kwargs):

    print args


# 执行方式一
func(name＝'wupeiqi',age=18)

# 执行方式二
li = {'name':'wupeiqi', age:18, 'gender':'male'}
func(**li)

def func(*args, **kwargs):

    print args
    print kwargs

扩展：发送邮件实例

import smtplib
from email.mime.text import MIMEText
from email.utils import formataddr
  
  
msg = MIMEText('邮件内容', 'plain', 'utf-8')
msg['From'] = formataddr(["武沛齐",'wptawy@126.com'])
msg['To'] = formataddr(["走人",'424662508@qq.com'])
msg['Subject'] = "主题"
  
server = smtplib.SMTP("smtp.126.com", 25)
server.login("wptawy@126.com", "邮箱密码")
server.sendmail('wptawy@126.com', ['424662508@qq.com',], msg.as_string())
server.quit()

内置函数：

 

 注：查看详细猛击这里

all(iterable)

#每个元素为真，它值为真，有一个假的为False。

Return True if all elements of the iterable are true (or if the iterable is empty). Equivalent to:

>>> print(all([0,-5,3]))
False

bytesarray()

a = bytes('abcde',encoding='utf-8')
b=bytearray('abcde',encoding='utf-8')  #把字符串转换为可修改的ascii码形式
print(b[0],b[1])
print(a.capitalize(),a)
b[1]=100
print(b)

callable() 可否调用

chr(),ord()

r=char(65)


    print(r)


    n=ord('B')


    print(n)

abs()  #绝对值

any()  #有一个值为真，其值为真。

ascii() #自动执行对象的__repr__方法

bin()

oct()

hex()

bytes()  字符串转字节

str()

用chr()的字母可以用随机的数字生成随机字母

ASCII中，大写字母数字范围为65-90  65-122(包括小写)

>>> str(bytes('李杰',encoding='utf-8'),encoding='utf-8')


    '李杰'

实例：随机验证码

random:


    import random


    i=random.randrange(1,5)


    print(i)

随机生成六个字母的验证码：

import random


    li=[]


    for i in range(6):


        temp=random.randrange(65,91)


        c=chr(temp)


        li.append(c)


    result="".join(li)    #拼接列表的字母


    print(result)

随机验证码2：

增加某一位或几位为随机数字：

import random


    li = []


    for i in range(6):


        if i == 2 or i == 4:


            num = random.randrange(0,10)


            li.append(str(num))


        else:


            temp = random.randrange(65, 91)


            c = chr(temp)


            li.append(c)


    result = "".join(li)  # 拼接列表的字母


    print(result)

在随机位置生成随机数字：

import random






    li = []


    for i in range(6):


        r =random.randrange(0,5)


        if r == 2 or r == 4:


            num = random.randrange(0,10)


            li.append(str(num))


        else:


            temp = random.randrange(65, 91)


            c = chr(temp)


            li.append(c)


    result = "".join(li)  # 拼接列表的字母


    print(result)

filter()和map()

    def f1(args):


        result=[]


        for item in args:


            if item>22:


                result.append(item)


        return result


    li=[11,22,33,44,55]


    ret=f1(li)


    print(ret)


    C:Python35python3.exe E:/ld/pythonclass/day3/testfilter.py


    [33, 44, 55]


    filter(函数，可迭代对象)  #在filter内部，循环第二个参数，且每次循环调用第一个函数。


    def f2(a):


        if a>22:


            return True


    li=[11,22,33,44,55]


    ret=filter(f2,li)   


    print(list(ret))


    C:Python35python3.exe E:/ld/pythonclass/day3/testfilter.py


    [33, 44, 55]

f1=lambda a:a>30


    ret=f1(90)


    print(ret)






    li=[11,22,33,44,55]


    result=filter(lambda a: a>33,li)


    print(list(result))


    C:Python35python3.exe E:/ld/pythonclass/day3/testfilter.py


    [44, 55]

map()（函数，可迭代的对象（可以for循环的东西）)


    li=[11,22,33,44,55]


    def f1(args):


        result=[]


        for i in args:


            result.append(100+i)


        return result


    r=f1(li)


    print(r)


    C:Python35python3.exe E:/ld/pythonclass/day3/testfilter.py


    [111, 122, 133, 144, 155]






    li=[11,22,33,44,55]


    def f2(a):


        return a+100


    result=map(f2,li)


    print(list(result))


    C:Python35python3.exe E:/ld/pythonclass/day3/testfilter.py


    [111, 122, 133, 144, 155]






    同上：


    li=[11,22,33,44,55]


    result=map(lambda a: a+100,li)


    print(list(result))

float():

format():

globals() #代表所有的全局变量

locals() #代表所有的局部变量

 

print(locals())


    print(globals())


    print(hash(s))

len():查看长度

max():

memoryview():查看内存地址的东西。

pow():求指数

range()

repr()

reverse():反转

round():四舍五入

slice():切片  #3.x新加的。

sorted():排序

staticmethod()

tuple()

type()

vars()

zip():混合列表内容

 >>> l1=['alex',11,22,33]


    >>> l2=['is',11,22,33]


    >>> l3=['sb',11,22,33]


    >>> zip(l1,l2)


    <zip object at 0x0386A508>


    >>> r=zip(l1,l2,l3)


    >>> print(list(r))


    [('alex', 'is', 'sb'), (11, 11, 11), (22, 22, 22), (33, 33, 33)]


    >>> r=zip(l1,l2,l3)


    >>> temp=list(r)[0]


    >>> ret=''.join(temp)


    >>> print(ret)


    alexissb

frozenset([iterable]):使可变类型不可变。

globals():返回当前文件的所有的变量，字典格式

compile()：把字符串编译成代码

编译时，模式可选择“single”,"eval","exec"

single:编译成单行的程序

evel:编译表达式

exec:编译成和python代码一模一样的代码

>>> code = 'for i in range(10):print(i)'
>>> code
'for i in range(10):print(i)'
>>> compile(code,'','exec')
<code object <module> at 0x01371840, file "", line 1>
>>> c=compile(code,'','exec')
>>> exec(c)

>>> code = "1+3/2*6"
>>> c=compile(code,'','eval')
>>> c
<code object <module> at 0x01371980, file "", line 1>
>>> eval(c)
10.0
>>> eval(code)
10.0

 eval():计算字符表达式

exec()：执行编译，可以直接执行字符串

eval()函数：

eval参数是一个字符串, 可以把这个字符串当成表达式来求值, 比如'x+1'就是一个表达式字符串 >>> x = 1 >>> print eval('x+1') 2

divmod()

>>> r=divmod(97,10)


    >>> print(r)


    (9, 7)


    or


    m,n=divmod(97,10)

dir(): #快速查看，对象提供了哪些功能

id(): 返回对象的唯一标识符，用整数表示。在程序生命周期内，这个标识符常量是唯一的。

isinstance():  #判断是否是一个类的实例

enumerate() 函数用于遍历序列中的元素以及它们的下标：

>>> for i,j in enumerate(('a','b','c')):


     print i,j


     0 a


    1 b


    2 c


    >>> for i,j in enumerate([1,2,3]):


     print i,j


     0 1


    1 2


    2 3


    >>> for i,j in enumerate({'a':1,'b':2}):


     print i,j


     


    0 a


    1 b


    >>> for i,j in enumerate('abc'):


     print i,j


     0 a


    1 b


    2 c

hash():给变量对应有序的数值。

locals():查找local变量

repr():

reversed()

round():截断

slice():切片

sorted():排序

a={6:2,8:0,1:4,-5:6,99:11,4:22}
print(sorted(a.items()))
print(sorted(a.items(),key=lambada x:x[1])) #按字典值排序

zip()

a=[1,2,3,4]
b=['a','b','c','d']
for i in zip(a,b):
    print(i)
C:Python35python3.exe E:/python34foexam/lessons/inside_func.py
(1, 'a')
(2, 'b')
(3, 'c')
(4, 'd')

__import__('decorator)

open函数，该函数用于文件处理

操作文件时，一般需要经历如下步骤：

• 打开文件
• 操作文件

一、打开文件

对文件操作流程

1. 打开文件，得到文件句柄并赋值给一个变量
2. 通过句柄对文件进行操作
3. 关闭文件 

文件句柄 = open('文件路径', '模式')

打开文件时，需要指定文件路径和以何等方式打开文件，打开后，即可获取该文件句柄，日后通过此文件句柄对该文件操作。

打开文件的模式有：

• r ，只读模式【默认】
• w，只写模式【不可读；不存在则创建；存在则清空内容；】
• x， 只写模式【不可读；不存在则创建，存在则报错】
• a， 追加模式【可读；   不存在则创建；存在则只追加内容；】

"+" 表示可以同时读写某个文件

• r+， 读写【可读，可写】
• w+，写读【可读，可写】
• x+ ，写读【可读，可写】
• a+， 写读【可读，可写】

"U"表示在读取时，可以将 自动转换成 （与 r 或 r+ 模式同使用）

• rU
• r+U

 "b"表示以字节的方式操作

• rb  或 r+b
• wb 或 w+b
• xb 或 w+b
• ab 或 a+b

 注：以b方式打开时，读取到的内容是字节类型，写入时也需要提供字节类型

二、操作

现有文件如下

Somehow, it seems the love I knew was always the most destructive kind
不知为何，我经历的爱情总是最具毁灭性的的那种
Yesterday when I was young
昨日当我年少轻狂
The taste of life was sweet
生命的滋味是甜的
As rain upon my tongue
就如舌尖上的雨露
I teased at life as if it were a foolish game
我戏弄生命 视其为愚蠢的游戏
The way the evening breeze
就如夜晚的微风
May tease the candle flame
逗弄蜡烛的火苗
The thousand dreams I dreamed
我曾千万次梦见
The splendid things I planned
那些我计划的绚丽蓝图
I always built to last on weak and shifting sand
但我总是将之建筑在易逝的流沙上
I lived by night and shunned the naked light of day
我夜夜笙歌 逃避白昼赤裸的阳光
And only now I see how the time ran away
事到如今我才看清岁月是如何匆匆流逝
Yesterday when I was young
昨日当我年少轻狂
So many lovely songs were waiting to be sung
有那么多甜美的曲儿等我歌唱
So many wild pleasures lay in store for me
有那么多肆意的快乐等我享受
And so much pain my eyes refused to see
还有那么多痛苦 我的双眼却视而不见
I ran so fast that time and youth at last ran out
我飞快地奔走 最终时光与青春消逝殆尽
I never stopped to think what life was all about
我从未停下脚步去思考生命的意义
And every conversation that I can now recall
如今回想起的所有对话
Concerned itself with me and nothing else at all
除了和我相关的 什么都记不得了
The game of love I played with arrogance and pride
我用自负和傲慢玩着爱情的游戏
And every flame I lit too quickly, quickly died
所有我点燃的火焰都熄灭得太快
The friends I made all somehow seemed to slip away
所有我交的朋友似乎都不知不觉地离开了
And only now I'm left alone to end the play, yeah
只剩我一个人在台上来结束这场闹剧
Oh, yesterday when I was young
噢 昨日当我年少轻狂
So many, many songs were waiting to be sung
有那么那么多甜美的曲儿等我歌唱
So many wild pleasures lay in store for me
有那么多肆意的快乐等我享受
And so much pain my eyes refused to see
还有那么多痛苦 我的双眼却视而不见
There are so many songs in me that won't be sung
我有太多歌曲永远不会被唱起
I feel the bitter taste of tears upon my tongue
我尝到了舌尖泪水的苦涩滋味
The time has come for me to pay for yesterday
终于到了付出代价的时间 为了昨日
When I was young
当我年少轻狂

基本操作　

f = open('lyrics') #打开文件
first_line = f.readline()
print('first line:',first_line) #读一行
print('我是分隔线'.center(50,'-'))
data = f.read()# 读取剩下的所有内容,文件大时不要用
print(data) #打印文件
 
f.close() #关闭文件

class file(object)
    def close(self): # real signature unknown; restored from __doc__
        关闭文件
        """
        close() -> None or (perhaps) an integer.  Close the file.
         
        Sets data attribute .closed to True.  A closed file cannot be used for
        further I/O operations.  close() may be called more than once without
        error.  Some kinds of file objects (for example, opened by popen())
        may return an exit status upon closing.
        """
 
    def fileno(self): # real signature unknown; restored from __doc__
        文件描述符  
         """
        fileno() -> integer "file descriptor".
         
        This is needed for lower-level file interfaces, such os.read().
        """
        return 0    
 
    def flush(self): # real signature unknown; restored from __doc__
        刷新文件内部缓冲区
        """ flush() -> None.  Flush the internal I/O buffer. """
        pass
 
 
    def isatty(self): # real signature unknown; restored from __doc__
        判断文件是否是同意tty设备
        """ isatty() -> true or false.  True if the file is connected to a tty device. """
        return False
 
 
    def next(self): # real signature unknown; restored from __doc__
        获取下一行数据，不存在，则报错
        """ x.next() -> the next value, or raise StopIteration """
        pass
 
    def read(self, size=None): # real signature unknown; restored from __doc__
        读取指定字节数据
        """
        read([size]) -> read at most size bytes, returned as a string.
         
        If the size argument is negative or omitted, read until EOF is reached.
        Notice that when in non-blocking mode, less data than what was requested
        may be returned, even if no size parameter was given.
        """
        pass
 
    def readinto(self): # real signature unknown; restored from __doc__
        读取到缓冲区，不要用，将被遗弃
        """ readinto() -> Undocumented.  Don't use this; it may go away. """
        pass
 
    def readline(self, size=None): # real signature unknown; restored from __doc__
        仅读取一行数据
        """
        readline([size]) -> next line from the file, as a string.
         
        Retain newline.  A non-negative size argument limits the maximum
        number of bytes to return (an incomplete line may be returned then).
        Return an empty string at EOF.
        """
        pass
 
    def readlines(self, size=None): # real signature unknown; restored from __doc__
        读取所有数据，并根据换行保存值列表
        """
        readlines([size]) -> list of strings, each a line from the file.
         
        Call readline() repeatedly and return a list of the lines so read.
        The optional size argument, if given, is an approximate bound on the
        total number of bytes in the lines returned.
        """
        return []
 
    def seek(self, offset, whence=None): # real signature unknown; restored from __doc__
        指定文件中指针位置
        """
        seek(offset[, whence]) -> None.  Move to new file position.
         
        Argument offset is a byte count.  Optional argument whence defaults to
(offset from start of file, offset should be >= 0); other values are 1
        (move relative to current position, positive or negative), and 2 (move
        relative to end of file, usually negative, although many platforms allow
        seeking beyond the end of a file).  If the file is opened in text mode,
        only offsets returned by tell() are legal.  Use of other offsets causes
        undefined behavior.
        Note that not all file objects are seekable.
        """
        pass
 
    def tell(self): # real signature unknown; restored from __doc__
        获取当前指针位置
        """ tell() -> current file position, an integer (may be a long integer). """
        pass
 
    def truncate(self, size=None): # real signature unknown; restored from __doc__
        截断数据，仅保留指定之前数据
        """
        truncate([size]) -> None.  Truncate the file to at most size bytes.
         
        Size defaults to the current file position, as returned by tell().
        """
        pass
 
    def write(self, p_str): # real signature unknown; restored from __doc__
        写内容
        """
        write(str) -> None.  Write string str to file.
         
        Note that due to buffering, flush() or close() may be needed before
        the file on disk reflects the data written.
        """
        pass
 
    def writelines(self, sequence_of_strings): # real signature unknown; restored from __doc__
        将一个字符串列表写入文件
        """
        writelines(sequence_of_strings) -> None.  Write the strings to the file.
         
        Note that newlines are not added.  The sequence can be any iterable object
        producing strings. This is equivalent to calling write() for each string.
        """
        pass
 
    def xreadlines(self): # real signature unknown; restored from __doc__
        可用于逐行读取文件，非全部
        """
        xreadlines() -> returns self.
         
        For backward compatibility. File objects now include the performance
        optimizations previously implemented in the xreadlines module.
        """
        pass

class TextIOWrapper(_TextIOBase):
    """
    Character and line based layer over a BufferedIOBase object, buffer.
    
    encoding gives the name of the encoding that the stream will be
    decoded or encoded with. It defaults to locale.getpreferredencoding(False).
    
    errors determines the strictness of encoding and decoding (see
    help(codecs.Codec) or the documentation for codecs.register) and
    defaults to "strict".
    
    newline controls how line endings are handled. It can be None, '',
    '
', '
', and '
'.  It works as follows:
    
    * On input, if newline is None, universal newlines mode is
      enabled. Lines in the input can end in '
', '
', or '
', and
      these are translated into '
' before being returned to the
      caller. If it is '', universal newline mode is enabled, but line
      endings are returned to the caller untranslated. If it has any of
      the other legal values, input lines are only terminated by the given
      string, and the line ending is returned to the caller untranslated.
    
    * On output, if newline is None, any '
' characters written are
      translated to the system default line separator, os.linesep. If
      newline is '' or '
', no translation takes place. If newline is any
      of the other legal values, any '
' characters written are translated
      to the given string.
    
    If line_buffering is True, a call to flush is implied when a call to
    write contains a newline character.
    """
    def close(self, *args, **kwargs): # real signature unknown
        关闭文件
        pass

    def fileno(self, *args, **kwargs): # real signature unknown
        文件描述符  
        pass

    def flush(self, *args, **kwargs): # real signature unknown
        刷新文件内部缓冲区
        pass

    def isatty(self, *args, **kwargs): # real signature unknown
        判断文件是否是同意tty设备
        pass

    def read(self, *args, **kwargs): # real signature unknown
        读取指定字节数据
        pass

    def readable(self, *args, **kwargs): # real signature unknown
        是否可读
        pass

    def readline(self, *args, **kwargs): # real signature unknown
        仅读取一行数据
        pass

    def seek(self, *args, **kwargs): # real signature unknown
        指定文件中指针位置
        pass

    def seekable(self, *args, **kwargs): # real signature unknown
        指针是否可操作
        pass

    def tell(self, *args, **kwargs): # real signature unknown
        获取指针位置
        pass

    def truncate(self, *args, **kwargs): # real signature unknown
        截断数据，仅保留指定之前数据
        pass

    def writable(self, *args, **kwargs): # real signature unknown
        是否可写
        pass

    def write(self, *args, **kwargs): # real signature unknown
        写内容
        pass

    def __getstate__(self, *args, **kwargs): # real signature unknown
        pass

    def __init__(self, *args, **kwargs): # real signature unknown
        pass

    @staticmethod # known case of __new__
    def __new__(*args, **kwargs): # real signature unknown
        """ Create and return a new object.  See help(type) for accurate signature. """
        pass

    def __next__(self, *args, **kwargs): # real signature unknown
        """ Implement next(self). """
        pass

    def __repr__(self, *args, **kwargs): # real signature unknown
        """ Return repr(self). """
        pass

    buffer = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    closed = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    encoding = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    errors = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    line_buffering = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    name = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    newlines = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    _CHUNK_SIZE = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

    _finalizing = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default

def close(self): # real signature unknown; restored from __doc__
        """
        Close the file.
        
        A closed file cannot be used for further I/O operations.  close() may be
        called more than once without error.
        """
        pass

    def fileno(self, *args, **kwargs): # real signature unknown
        """ Return the underlying file descriptor (an integer). """
        pass

    def isatty(self, *args, **kwargs): # real signature unknown
        """ True if the file is connected to a TTY device. """
        pass

    def read(self, size=-1): # known case of _io.FileIO.read
        """
        注意，不一定能全读回来
        Read at most size bytes, returned as bytes.
        
        Only makes one system call, so less data may be returned than requested.
        In non-blocking mode, returns None if no data is available.
        Return an empty bytes object at EOF.
        """
        return ""

    def readable(self, *args, **kwargs): # real signature unknown
        """ True if file was opened in a read mode. """
        pass

    def readall(self, *args, **kwargs): # real signature unknown
        """
        Read all data from the file, returned as bytes.
        
        In non-blocking mode, returns as much as is immediately available,
        or None if no data is available.  Return an empty bytes object at EOF.
        """
        pass

    def readinto(self): # real signature unknown; restored from __doc__
        """ Same as RawIOBase.readinto(). """
        pass #不要用,没人知道它是干嘛用的

    def seek(self, *args, **kwargs): # real signature unknown
        """
        Move to new file position and return the file position.
        
        Argument offset is a byte count.  Optional argument whence defaults to
        SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values
        are SEEK_CUR or 1 (move relative to current position, positive or negative),
        and SEEK_END or 2 (move relative to end of file, usually negative, although
        many platforms allow seeking beyond the end of a file).
        
        Note that not all file objects are seekable.
        """
        pass

    def seekable(self, *args, **kwargs): # real signature unknown
        """ True if file supports random-access. """
        pass

    def tell(self, *args, **kwargs): # real signature unknown
        """
        Current file position.
        
        Can raise OSError for non seekable files.
        """
        pass

    def truncate(self, *args, **kwargs): # real signature unknown
        """
        Truncate the file to at most size bytes and return the truncated size.
        
        Size defaults to the current file position, as returned by tell().
        The current file position is changed to the value of size.
        """
        pass

    def writable(self, *args, **kwargs): # real signature unknown
        """ True if file was opened in a write mode. """
        pass

    def write(self, *args, **kwargs): # real signature unknown
        """
        Write bytes b to file, return number written.
        
        Only makes one system call, so not all of the data may be written.
        The number of bytes actually written is returned.  In non-blocking mode,
        returns None if the write would block.
        """
        pass
复制代码

with语句

为了避免打开文件后忘记关闭，可以通过管理上下文，即：

with open('log','r') as f:

     

    ...

如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。

在Python 2.7 后，with又支持同时对多个文件的上下文进行管理，即：

1 2	with open('log1') as obj1, open('log2') as obj2:     pass

三、管理上下文

为了避免打开文件后忘记关闭，可以通过管理上下文，即：

1 2 3

with open('log','r') as f:              ...

如此方式，当with代码块执行完毕时，内部会自动关闭并释放文件资源。

在Python 2.7 及以后，with又支持同时对多个文件的上下文进行管理，即：

with open('log1') as obj1, open('log2') as obj2:
    pass

程序练习　　

程序1: 实现简单的shell sed替换功能

程序2:修改haproxy配置文件 

 

 

lambda表达式:

学习条件运算时，对于简单的 if else 语句，可以使用三元运算来表示，即：

# 普通条件语句
if 1 == 1:
    name = 'wupeiqi'
else:
    name = 'alex'
    
# 三元运算
name = 'wupeiqi' if 1 == 1 else 'alex'

对于简单的函数，也存在一种简便的表示方式，即：lambda表达式

# ###################### 普通函数 ######################
# 定义函数（普通方式）
def func(arg):
    return arg + 1
    
# 执行函数
result = func(123)
    
# ###################### lambda ######################
    
# 定义函数（lambda表达式）
my_lambda = lambda arg : arg + 1
    
# 执行函数
result = my_lambda(123)

lambada带参数

calc=lambda n:print(n)
calc(5)  或者 (lambda n:print(n))(5)

递归

利用函数编写如下数列：

斐波那契数列指的是这样一个数列 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233，377，610，987，1597，2584，4181，6765，10946，17711，28657，46368...

def func(arg1,arg2):
    if arg1 == 0:
        print arg1, arg2
    arg3 = arg1 + arg2
    print arg3
    func(arg2, arg3)
  
func(0,1)

练习题

1、简述普通参数、指定参数、默认参数、动态参数的区别

2、写函数，计算传入字符串中【数字】、【字母】、【空格] 以及 【其他】的个数

3、写函数，判断用户传入的对象（字符串、列表、元组）长度是否大于5。

4、写函数，检查用户传入的对象（字符串、列表、元组）的每一个元素是否含有空内容。

5、写函数，检查传入列表的长度，如果大于2，那么仅保留前两个长度的内容，并将新内容返回给调用者。

6、写函数，检查获取传入列表或元组对象的所有奇数位索引对应的元素，并将其作为新列表返回给调用者。

7、写函数，检查传入字典的每一个value的长度,如果大于2，那么仅保留前两个长度的内容，并将新内容返回给调用者。

1 2 3

dic = {"k1": "v1v1", "k2": [11,22,33,44]}   PS:字典中的value只能是字符串或列表

8、写函数，利用递归获取斐波那契数列中的第 10 个数，并将该值返回给调用者。