python基础（内置函数+文件操作+lambda）

一、内置函数

注：查看详细猛击这里

常用内置函数代码说明:

 # abs绝对值
 # i = abs(-123)
 # print(i)  #返回123，绝对值

 # #all，循环参数，如果每个元素为真，那么all返回的为真，有一个为假返回的就是假的
 # a = all((None,123,456,False))
 # print(a)   #返回的为假的，证明中间有False值
 #
 # #所有的假值有
 #     #0，None,空值
 #

 # #any  只要之前有一个是真的，返回的就是真
 # b = any([11,False])
 # print(b)

 #ascii，去指定对象的类中找__repr__,获取返回值
 # #ascii函数
 # class Foo:
 #     def __repr__(self):
 #         return "tina"
 # obj =Foo()
 # r = ascii(obj)
 # print(r)

 # 布尔值返回真或假
 # print(bool(1))
 # print(bool(0))

 # #bin二进制
 # r = bin(123)
 # print(r)

 # #oct八进制
 # r = oct(123)
 # print(r)

 # #int十进制
 # r = int(123)
 # print(r)

 # #hex十六进制
 # r = hex(123)
 # print(r)

 # #二进制转十进制
 # i= int("0b11",base=2)
 # print(i)

 # #八进制转十进制
 # i= int("11",base=8)
 # print(i)

 # #十六进制转十进制
 # i = int("0xe",base=16)
 # print(i)
  
#  bin oct int hex   二进制  八进制  十进制  十六进制
# bin() 可以将 八 十 十六 进制 转换成二进制
print(bin(10),bin(0o13),bin(0x14))
# oct() 可以将 二 十 十六 进制 转换为八进制
print(oct(10),oct(0b101),oct(0x14))
# int() 可以将 二 八 十六进制转换为十进制
print(int(0o13),int(0b101),int(0x14))
# hex() 可以将 二 八 十 进制转换为十六进制
print(hex(0b101),hex(110),hex(0o12))

 # #数字代表字母
 # c = chr(66)chr()输入数字，找到ascii码对应的字母
 # print(c)

 # #字母代表数字
 # c = ord("a")
 # print(c)

 #bytes,  字节
 #字节和字符串的转换
 # a = bytes("tina",encoding="utf-8")
 # print(a)
 #bytearray  字节列表

 #chr(),把数字转换成字母,只适用于ascii码
 # a = chr(65)
 # print(a)

 #ord(),把字母转换成数字，只适用于ascii码
 # a = ord("a")
 # print(a)

 #callable表示一个对象是否可执行
 # def f1():        #看这个函数能不能执行，能则返回True
 #     return 123
 # f1()
 # r = callable(f1)
 # print(r)

 #dir,查看一个类里面存在的功能
 # li = []
 # print(dir(li))
 # help(list)

 #divmod(),#分页的时候使用
 # a = 10/3
 # r = divmod(10,3)
 # print(r)

 #compile编译, 把字符串转移成python可执行的代码，知道就行

 #eval(),简单的表达式，可以给算出来
 # b = eval("a + 69" , {"a":99})  #a可以通过字典声明变量去写入
 # print(b)

 #exec,不会返回值，直接输出结果
 # exec("for i in range(10):print(i)")

 # filter对于序列中的元素进行筛选，最终获取符合条件的序列（需要循环）
 # def f1(x):
 #     if x >22:
 #         return  True
 #     else:
 #         return False
 #
 # ret = filter(f1,[11,22,33,44,55])
 # for i in ret:
 #     print(i)

 # ret = filter(lambda x: x > 22, [11, 22, 33, 44, 55, 66, 77])
 # for i in ret:
 #     print(i)

 #map(函数，可以迭代的对象，让元素统一操作)
 # def f1(x):
 #     return x+123
 #
 # # li = [11,22,33,44,55,66]
 # # ret = map(f1,li)
 # print(ret)
 # for i in ret:
 #     print(i)
 #
 # ret = map(lambda x: x + 100 if x%2==1 else x, [11, 22, 33, 44])
 # print(ret)
 # for i in ret:
 #     print(i)

 #globals()获取当前所有的全局变量

 #locals（）获取当前所有的局部变量
 # ret = "asziusdhf"
 # def fu1():
 #     name = 123
 #     print(locals())
 #     print(globals())
 #
 # fu1()

 #hash 对key的优化，相当于给输出一种哈希值
 # li = "sdglgmdgongoaerngonaeorgnienrg"
 # print(hash(li))

 #isinstance()判断是不是一个类型
 # li = [11,22]
 # ret = isinstance(li,list)
 # print(ret)
############小案例#######################

def obj_len(a):
    if isinstance(a,str) or isinstance(a,list) or isinstance(a,tuple):
        if len(a)>5:
            return True
        else:
            return False
    return None
t = [111,22,2,2,]
tt = obj_len(t)
print(tt)

 #iter创建一个可以被迭代的元素
 # obj = iter([11,22,33,44])
 # print(obj)
 # #next，取下一个值，一个变量里的值可以一直往下取，直到没有就报错
 # ret = next(obj)

 #max（）取最大的值
 # li = [11,22,33,44]
 # ret = max(li)
 # print(ret)

 #min()取最小值
 # li = [11,22,33,44]
 # ret = min(li)
 # print(ret)

 #求一个数字的多少次方
 # ret = pow(2,10)
 # print(ret)

 #reversed反转
 # a = [11,22,33,44]
 # b = reversed(a)
 # for i in b:
 #     print(i)

 #round 四舍五入
 # ret = round(4.8)
 # print(ret)

 #sum求和
 # ret = sum((11,22,33,44))
 # print(ret)

 #zip，1 1对应
 # li1 = [11,22,33,44,55]
 # li2 = [99,88,77,66,89]
 # dic = dict(zip(li1,li2))
 # print(dic)

 #sorted 排序
 # li = ["1","2sdg;l","57","a","b","A","中国人"]
 # lis = sorted(li)
 # print(lis)
 # for i in lis:
 #     print(bytes(i,encoding="utf-8"))
######################小案例：############################
 # #随机生成6位验证码
 # import random
 # temp = ''
 # for i in range(6):
 #     num = random.randrange(0,4)
 #     if num ==3 or num ==1:
 #         rad1 = random.randrange(0,10)
 #         temp+=str(rad1)
 #     else:
 #         rad2 = random.randrange(65,91)
 #         c1 = chr(rad2)
 #         temp+=c1
 # print(temp)

二、文件处理

1、打开文件

 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【不可读；   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】

"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

#普通方式打开
# ====python内部将二进制转换成字符串，通过字符串操作

#二进制打开方式
#用户自己操作把字符串转成二进制，然后让电脑识别

# 1. 只读模式，r
# a = open("1.log","r")   #打开1.log，赋予只读的权限
# ret = a.read()        #读取文件
# a.close()            #退出文件
# print(ret)             #打印文件内容

#2.只写模式，w, 如果不存在会创建文件，存在则清空内容
# a = open("3.log","w")
# a.write("sdfhsuigfhuisg")
# a.close()

#3.只写模式，x, 如果不存在会创建文件，存在则报错
# a = open("4.log","x")
# a.write("12345678")
# a.close()

#4.追加模式，a，不可读，不存在则创建文件，存在则会追加内容
# a = open("4.log","a")
# a.write("asjfioshf")
# a.close()

# "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）

#5.只读模式，rb,以字节方式打开，默认打开是字节的方式
# a = open("2.log","rb")    #二进制方式读取2.log文件
# date = a.read()            #定义变量，读文件
# a.close()                  #关闭文件
# print(date)                #打印文件
# str_data = str(date, encoding="utf-8")    #字节转换成utf-8
# print(str_data)            # 打印文件

#6.只写模式，wb，
# a = open("2.log","wb")     #打开文件2.log，可写的模式
# date = "中国人"             #定义字符串
# a.write(bytes(date , encoding="utf-8")) #转换成字节，方便计算机识别
# a.close()                    #关闭文件
# print(date)                  #打印出来

#7.只写模式，xb，
# a = open("6.log","xb")
# date = "哈哈哈"
# # a.write("sakfdhisf")   #字符串形式会报错，计算机不识别，得转换成字节
# a.write(bytes(date,encoding="utf-8"))
# a.close()
# print(date)

#8.追加模式，ab,
# a = open("5.log","ab")
# date = "呵呵呵"
# a.write(bytes(date,encoding="utf-8"))
# a.close()
# print(date)

# #"+"表示具有读写的功能

# #9.r+，读写（可读，可写）
# a = open("5.log","r+",encoding="utf-8")
# print(a.tell())    #打开文件后观看指针位置在第几位，默认在起始位置
#
# date = a.read()       #第一次读取,指针读取到最后了，（可以加读取的索引位置，3表示只看前三位）
# print(date)
#
# a.write("嘿嘿嘿")      #写的时候会把指针调到最后去写
#
# a.seek(0)           #把指针放在第一位进行第二次读取
#
# date = a.read()       #第二次读取
# print(date)
# a.close()
 
#10.w+，写读，（可写，可读）,先清空内容，在写之后需要把指针放在第一位才能读
# a = open("5.log","w+",encoding="utf-8")
# a.write("哦哦")        #清空内容写入“哦哦”
# a.seek(0)                 #把指针放在第一位
# date = a.read()           #进行读取
# a.close()                 #退出文件
# print(date)

#11.x+，写读，(可写，可读)，需要创建一个新文件，文件存在会报错，在写之后需要把指针放在第一位才能读
# a = open("7.log","x+",encoding="utf-8")
# a.write("嘻嘻嘻")        #清空内容写入“嘻嘻嘻”
# a.seek(0)                 #把指针放在第一位
# date = a.read()           #进行读取
# a.close()                 #退出文件
# print(date)

#12.a+，写读，(可写，可读)，打开文件的同时，指针已经在最后了
# a = open("5.log","a+",encoding="utf-8")
# date = a.read()          #第一次读，没数据，因为指针在最后
# print(date)
#
# a.write("嗯嗯")          #往最后写入 嗯嗯
#
# a.seek(0)                #把指针放在第一位，让他进行曲读
# date = a.read()
# print(date)
#
# a.close()

2、文件操作方法：

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

3.x

3.0

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

2.x

2.0

 a = open("5.log","r+",encoding="utf-8")
 # a.truncate()     #依赖于指针，截取数据，只剩下指针所在位置的前面的数据
 # a.close()        #关闭
 # a.flush()        #强行加入内存
 # a.read()         #读
 # a.readline()     #只读取第一行
 # a.seek(0)        #指针
 # a.tell()         #当前指针位置
 # a.write()        #写

3、文件上下文管理

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：

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

例：

1 2 3 4 5 6 7 8

#关闭文件with with open("5.log","r") as a:     a.read()   #同事打开两个文件,把a复制到b中，读一行写一行，直到写完 with open("5.log","r",encoding="utf-8") as a,open("6.log","w",encoding="utf-8") as b:     for line in a:         b.write(line)

三、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：

1 2 3 4 5 6 7 8

# 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

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# ###################### 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)