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:
1 # abs绝对值 2 # i = abs(-123) 3 # print(i) #返回123，绝对值 4 5 6 # #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 7 # a = all((None,123,456,False)) 8 # print(a) #返回的为假的，证明中间有False值 9 # 10 # #所有的假值有 11 # #0，None,空值 12 # 13 14 # #any 只要之前有一个是真的，返回的就是真 15 # b = any([11,False]) 16 # print(b) 17 18 19 #ascii，去指定对象的类中找__repr__,获取返回值 20 # #ascii函数 21 # class Foo: 22 # def __repr__(self): 23 # return "tina" 24 # obj =Foo() 25 # r = ascii(obj) 26 # print(r) 27 28 29 # 布尔值返回真或假 30 # print(bool(1)) 31 # print(bool(0)) 32 36 # #bin二进制 37 # r = bin(123) 38 # print(r) 39 40 # #oct八进制 41 # r = oct(123) 42 # print(r) 43 44 # #int十进制 45 # r = int(123) 46 # print(r) 47 48 # #hex十六进制 49 # r = hex(123) 50 # print(r) 51 52 # #二进制转十进制 53 # i= int("0b11",base=2) 54 # print(i) 55 56 # #八进制转十进制 57 # i= int("11",base=8) 58 # print(i) 59 60 # #十六进制转十进制 61 # i = int("0xe",base=16) 62 # print(i) 63
# 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))
64 # #数字代表字母 65 # c = chr(66)chr()输入数字，找到ascii码对应的字母 66 # print(c) 67 68 # #字母代表数字 69 # c = ord("a") 70 # print(c) 73 #bytes, 字节 74 #字节和字符串的转换 75 # a = bytes("tina",encoding="utf-8") 76 # print(a) 77 #bytearray 字节列表 81 #chr(),把数字转换成字母,只适用于ascii码 82 # a = chr(65) 83 # print(a) 84 85 #ord(),把字母转换成数字，只适用于ascii码 86 # a = ord("a") 87 # print(a) 88 89 #callable表示一个对象是否可执行 90 # def f1(): #看这个函数能不能执行，能则返回True 91 # return 123 92 # f1() 93 # r = callable(f1) 94 # print(r) 98 #dir,查看一个类里面存在的功能 99 # li = [] 100 # print(dir(li)) 101 # help(list) 102 103 104 #divmod(),#分页的时候使用 105 # a = 10/3 106 # r = divmod(10,3) 107 # print(r) 108 109 110 111 #compile编译, 把字符串转移成python可执行的代码，知道就行 112 113 #eval(),简单的表达式，可以给算出来 114 # b = eval("a + 69" , {"a":99}) #a可以通过字典声明变量去写入 115 # print(b) 116 117 #exec,不会返回值，直接输出结果 118 # exec("for i in range(10):print(i)") 119 120 121 # 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） 122 # def f1(x): 123 # if x >22: 124 # return True 125 # else: 126 # return False 127 # 128 # ret = filter(f1,[11,22,33,44,55]) 129 # for i in ret: 130 # print(i) 131 132 # ret = filter(lambda x: x > 22, [11, 22, 33, 44, 55, 66, 77]) 133 # for i in ret: 134 # print(i) 135 136 #map(函数，可以迭代的对象，让元素统一操作) 137 # def f1(x): 138 # return x+123 139 # 140 # # li = [11,22,33,44,55,66] 141 # # ret = map(f1,li) 142 # print(ret) 143 # for i in ret: 144 # print(i) 145 # 146 # ret = map(lambda x: x + 100 if x%2==1 else x, [11, 22, 33, 44]) 147 # print(ret) 148 # for i in ret: 149 # print(i) 150 151 #globals()获取当前所有的全局变量 152 153 #locals（）获取当前所有的局部变量 154 # ret = "asziusdhf" 155 # def fu1(): 156 # name = 123 157 # print(locals()) 158 # print(globals()) 159 # 160 # fu1() 161 162 163 #hash 对key的优化，相当于给输出一种哈希值 164 # li = "sdglgmdgongoaerngonaeorgnienrg" 165 # print(hash(li)) 166 167 #isinstance()判断是不是一个类型 168 # li = [11,22] 169 # ret = isinstance(li,list) 170 # 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)
173 #iter创建一个可以被迭代的元素 174 # obj = iter([11,22,33,44]) 175 # print(obj) 176 # #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 177 # ret = next(obj) 178 179 #max（）取最大的值 180 # li = [11,22,33,44] 181 # ret = max(li) 182 # print(ret) 183 184 #min()取最小值 185 # li = [11,22,33,44] 186 # ret = min(li) 187 # print(ret) 188 189 #求一个数字的多少次方 190 # ret = pow(2,10) 191 # print(ret) 192 193 #reversed反转 194 # a = [11,22,33,44] 195 # b = reversed(a) 196 # for i in b: 197 # print(i) 198 199 #round 四舍五入 200 # ret = round(4.8) 201 # print(ret) 202 203 #sum求和 204 # ret = sum((11,22,33,44)) 205 # print(ret) 206 207 #zip，1 1对应 208 # li1 = [11,22,33,44,55] 209 # li2 = [99,88,77,66,89] 210 # dic = dict(zip(li1,li2)) 211 # print(dic) 212 213 214 #sorted 排序 215 # li = ["1","2sdg;l","57","a","b","A","中国人"] 216 # lis = sorted(li) 217 # print(lis) 218 # for i in lis: 219 # print(bytes(i,encoding="utf-8")) ######################小案例：############################ 224 # #随机生成6位验证码 225 # import random 226 # temp = '' 227 # for i in range(6): 228 # num = random.randrange(0,4) 229 # if num ==3 or num ==1: 230 # rad1 = random.randrange(0,10) 231 # temp+=str(rad1) 232 # else: 233 # rad2 = random.randrange(65,91) 234 # c1 = chr(rad2) 235 # temp+=c1 236 # 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
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
1 a = open("5.log","r+",encoding="utf-8") 2 # 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 3 # a.close() #关闭 4 # a.flush() #强行加入内存 5 # a.read() #读 6 # a.readline() #只读取第一行 7 # a.seek(0) #指针 8 # a.tell() #当前指针位置 9 # 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：
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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：
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with open('log1') as obj1, open('log2') as obj2: pass |
例：
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#关闭文件withwith 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：
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# 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) |
