Python学习路程day3

set集合

​set是一个无序且不重复的元素集合,访问速度快，天生解决重复问题

s1 = set()

s1.add('luo')​

s2 = set (['luo','wu','wei','ling'])

​s3 = s2.difference(['luo','wu'])            #s2中数据拿来逐个匹配，不同的被赋值给s3

​s2.difference_update(['luo','wu'])       #s2数据逐个匹配，修改s2

difference:不修改原来集合，创建一个新的集合

difference_update:修改原集合，不需要赋值，如赋值，返回值为None

s2.pop()         #随机删除一个数据​，没有返回值

s2.remove('luo')     #移除数据luo，可以赋值给变量​

例：​

​# 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 }

​​}

​old = set(old_dict.keys())

new = set(new_dict.keys())​

交集：​把old和new相同的元素取出来赋值给update_set

update_set = old.intersection(new)

差集：​从old中拿出和update_set相同的数据，old中不同的数值赋值给delete

delete_set = old.difference(update_set)​​

add_set = new.difference(update_set)​

对称差：把new和update_set不同的都拿出来

​delete_set = old.symmetric_difference(update_set)​​

add_set = new.symmetric_difference(update_set)​

collections​

​一、计数器（counter）

Counter是对字典类型的补充，用于追踪值的出现次数​

ps：具备字典的所有功能 + 自己的功能

import collections​

c = collections​.Counter('abcdeabcdabcaba')

print c

输出：Counter({'a': 5, 'b': 4, 'c': 3, 'd': 2, 'e': 1})

c.update(['eric','11','11'])​ #添加元素到变量c

c.subtract(['11','eric'])​   #删除变量c里面的这些元素

​for k in c.elements():                 #elements是元素，取出里面所有元素

print (k)

for k,v in c.items():                    #取key和values

print (k,v)​

二、有序字典​

函数​

def 函数名(参数):    

    ...

    函数体

    ...

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。return是关键字，默认为None，return以下的代码是不会执行的

def show():

　　print('a')

　　return 123          #返回值是123，下面的print（'b')不会执行

　　print('b')​

​f = show()​​​

print (f​)             #会有'a'和123

函数的普通参数

user为形式参数，最后面的mail()括号的为实际参数

#!/usr/bin/env python
import smtplib
from email.mime.text import MIMEText
from email.utils import formataddr
def mail(user):
    ret = True
    try:
        msg = MIMEText('邮件内容','plain','utf-8')
        msg['From'] = formataddr(['武沛齐','[e-mail]'])
        msg['To'] = formataddr(['走人','[e-mail]'])
        msg['Subject'] = '主题'
        server = smtplib.SMTP("smtp.126.com",25)
        server.login("[e-mail]","WW.3945.59")
        server.sendmail("[e-mail]",[user,],msg.as_string())
        server.quit()
    except Exception:
        ret = False
    return ret
ret = mail('[e-mail]')          #输入要发送的用户名
if ret:
    print("发送成功")
else:
    print("发送失败")

多个参数

#!/usr/bin/env python

#一个参数
def show(arg):
    print (arg)
show("kkkkkk")

#两个参数
def show(arg,xxx):
    print (arg,xxx)
show("kkkkkk","")

函数的默认参数：

默认参数必须放在最后，如果给a2赋值，那么a2的默认值会被覆盖

def show(a1,a2=999):
    print (a1,a2)
show(111)
show(111,888)

指定参数：

def show(a1,a2):
    print (a1,a2)
show (a2=123,a1=999)

函数的动态参数：

实际参数可以是“元组”，“列表”，"字典"

一个"*"默认是”元组"

两个"*"默认是”字典“

def show(*arg):
    print (arg,type(arg))
show(1,2,3,4,5,6)
>>>(1,2,3,4,5,6)<class 'tuple'>

def show(**arg):
    print (arg,type(arg))
show (n1=78,uu=123,bb=999)
>>>{'bb':999,'n1':78,'uu':123}<class'dict'>

还可以“*”，“**”组合使用，"**"必须放在“*”后面

def show(*args,**kwargs):
    print (args,type(args))
    print (kwargs,type(kwargs))
show (11,22,33,44,n1=88,luo='stupid')

如果要把一个字典和一个列表分别放进（*arg和**kwargs），就分别在字典和列表的变量加对应的*和**,如果没有加，那么都会放进args里。

def show(*args,**kwargs):
    print (args,type(args))
    print (kwargs,type(kwargs))
l = [,,,]
d = {'n1':,'luo':'stupid'}
show(*l,**d)

动态参数实现字符串格式化：

可以直接在括号里加参数，也可以用list和dict来实现。

s1 = "{0} is {1}"            #必须使用0和1
l = ['luo','stupid']
result = s1.format(*l)       #返回值赋给result
print (result)

s1 = "{name} is {acter}"
d = {'name':'luo','acter':'stupid'}
result = s1.format(**d)
print (result)

lambda表达式：

简单函数的简单表示

func = lambda  a: a+        #a是形式参数，可以是多个，冒号后面是函数体，并且返回return值
ret = func()
print (ret)

#传统函数表达方式
def func(a):
    a +=1
    return a
result = func(99)
print (result)

常用内置函数：

enumerate()

l = ['luo','ling','feng']
for i,item in enumerate(l,):               #结果加上序号，从1开始
    print (i,item)

all()：如果传入的所有元素都为真，才为真

bool():布尔值，None为假，空字符串，元组，列表，字典都为假

any():只要有一个元素是真，返回值为真

bin():二进制，将数字转换为二进制

bytearray():转换成字节数组

bytes():转换成字符串

callbable():检查对象object是否可调用。如果返回True，object仍然可能调用失败；但如果返回False，调用对象ojbect绝对不会成功

chr():将数字转为asci码里的字符（一般用于随机验证码）

ord():将asci码的字符转换为数字（一般用于随机验证码）

dir():不带参数时，返回当前范围内的变量、方法和定义的类型列表；带参数时，返回参数的属性、方法列表

eval():将字符串str当成有效的表达式来求值并返回计算结果。例：左边的数据和右边的数据相乘，eval("6*8")

filter():对于序列中的元素进行筛选，最终获取符合条件的序列

li = [,,,]
def func(x):
    if x>:
        return True
    else:
        return False
n = filter(func,li)
print (list(n))
>>>[44]

map():遍历序列，对序列中每个元素进行操作，最终获取新的序列

li = [,,,]
new_li = map(lambda x:x+,li)
l = list(new_li)
print (l)
>>>[111,122,133,144]

open函数

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

1	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；存在则删除内容；】
• 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+，可读写文件。【可读；可写；可追加】
• w+，写读
• a+，同a

"U"表示在读取时，可以将 \r \n \r\n自动转换成 \n （与 r 或 r+ 模式同使用）

• rU
• r+U

"b"表示处理二进制文件（如：FTP发送上传ISO镜像文件，linux可忽略，windows处理二进制文件时需标注）

• rb
• wb
• ab

二、操作

f.tell()     #查看当前指针位置

f.seek()    #指定当前指针位置

f.read()    #指定读取字符

f.truncate() #保留指针前面的内容，并且删除原文件指针之后的内容

python 3.x中read按字符读取，tell按字节查看。

python 2.x

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

Python 2.x

python 3.x

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, '',
    '\n', '\r', and '\r\n'.  It works as follows:

    * On input, if newline is None, universal newlines mode is
      enabled. Lines in the input can end in '\n', '\r', or '\r\n', and
      these are translated into '\n' 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 '\n' characters written are
      translated to the system default line separator, os.linesep. If
      newline is '' or '\n', no translation takes place. If newline is any
      of the other legal values, any '\n' 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

Python 3.x