1.3.2 常用内置函数
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常用内置函数（Built-In Functions,BIF）不需要导入任何模块即可直接使用，在IDLE中执行如下命令可以列出所有内置函数和内置对象，如代码块1.3.2.1所示：
1 >>> dir(__builtins__) 2 [\'ArithmeticError\', \'AssertionError\', \'AttributeError\', \'BaseException\', \'BlockingIOError\', \'BrokenPipeError\', \'BufferError\',
\'BytesWarning\', \'ChildProcessError\', \'ConnectionAbortedError\', \'ConnectionError\', \'ConnectionRefusedError\', \'ConnectionResetError\',
\'DeprecationWarning\', \'EOFError\', \'Ellipsis\', \'EnvironmentError\', \'Exception\', \'False\', \'FileExistsError\', \'FileNotFoundError\',
\'FloatingPointError\', \'FutureWarning\', \'GeneratorExit\', \'IOError\', \'ImportError\', \'ImportWarning\', \'IndentationError\', \'IndexError\',
\'InterruptedError\', \'IsADirectoryError\', \'KeyError\', \'KeyboardInterrupt\', \'LookupError\', \'MemoryError\', \'NameError\', \'None\',
\'NotADirectoryError\', \'NotImplemented\', \'NotImplementedError\', \'OSError\', \'OverflowError\', \'PendingDeprecationWarning\',
\'PermissionError\', \'ProcessLookupError\', \'RecursionError\', \'ReferenceError\', \'ResourceWarning\', \'RuntimeError\', \'RuntimeWarning\',
\'StopAsyncIteration\', \'StopIteration\', \'SyntaxError\', \'SyntaxWarning\', \'SystemError\', \'SystemExit\', \'TabError\', \'TimeoutError\', \'True\',
\'TypeError\', \'UnboundLocalError\', \'UnicodeDecodeError\', \'UnicodeEncodeError\', \'UnicodeError\', \'UnicodeTranslateError\', \'UnicodeWarning\',
\'UserWarning\', \'ValueError\', \'Warning\', \'WindowsError\', \'ZeroDivisionError\', \'__build_class__\', \'__debug__\', \'__doc__\', \'__import__\',
\'__loader__\', \'__name__\', \'__package__\', \'__spec__\', \'abs\', \'all\', \'any\', \'ascii\', \'bin\', \'bool\', \'bytearray\', \'bytes\',
\'callable\', \'chr\', \'classmethod\', \'compile\', \'complex\', \'copyright\', \'credits\', \'delattr\', \'dict\', \'dir\', \'divmod\',
\'enumerate\', \'eval\', \'exec\', \'exit\', \'filter\', \'float\', \'format\', \'frozenset\', \'getattr\', \'globals\', \'hasattr\',
\'hash\', \'help\', \'hex\', \'id\', \'input\', \'int\', \'isinstance\', \'issubclass\', \'iter\', \'len\', \'license\', \'list\', \'locals\', \'map\',
\'max\', \'memoryview\', \'min\', \'next\', \'object\', \'oct\', \'open\', \'ord\', \'pow\', \'print\', \'property\', \'quit\', \'range\', \'repr\',
\'reversed\', \'round\', \'set\', \'setattr\', \'slice\', \'sorted\', \'staticmethod\', \'str\', \'sum\', \'super\', \'tuple\', \'type\', \'vars\', \'zip\'] 3 >>>
代码块1.3.2.1
可以使用 help(函数名) 查看某个函数的用法，不需要导入模块就可以直接使用 help(模块名)查看该模块的帮助文档，例如 help(\'math\')。help()函数示例，参考代码块1.3.2.2
1 >>> help(abs) 2 Help on built-in function abs in module builtins: 3 4 abs(x, /) 5 Return the absolute value of the argument. 6 7 >>> 8 >>> 9 >>> help(math) 10 Traceback (most recent call last): 11 File "<pyshell#8>", line 1, in <module> 12 help(math) 13 NameError: name \'math\' is not defined 14 >>> 15 >>> help(\'math\') 16 Help on built-in module math: 17 18 NAME 19 math 20 21 DESCRIPTION 22 This module is always available. It provides access to the 23 mathematical functions defined by the C standard. 24 25 FUNCTIONS 26 acos(...) 27 acos(x) 28 29 Return the arc cosine (measured in radians) of x. 30 31 acosh(...) 32 acosh(x) 33 34 Return the inverse hyperbolic cosine of x. 35 36 asin(...) 37 asin(x) 38 39 Return the arc sine (measured in radians) of x. 40 41 asinh(...) 42 asinh(x) 43 44 Return the inverse hyperbolic sine of x. 45 46 atan(...) 47 atan(x) 48 49 Return the arc tangent (measured in radians) of x. 50 51 atan2(...) 52 atan2(y, x) 53 54 Return the arc tangent (measured in radians) of y/x. 55 Unlike atan(y/x), the signs of both x and y are considered. 56 57 atanh(...) 58 atanh(x) 59 60 Return the inverse hyperbolic tangent of x. 61 62 ceil(...) 63 ceil(x) 64 65 Return the ceiling of x as an Integral. 66 This is the smallest integer >= x. 67 68 copysign(...) 69 copysign(x, y) 70 71 Return a float with the magnitude (absolute value) of x but the sign 72 of y. On platforms that support signed zeros, copysign(1.0, -0.0) 73 returns -1.0. 74 75 cos(...) 76 cos(x) 77 78 Return the cosine of x (measured in radians). 79 80 cosh(...) 81 cosh(x) 82 83 Return the hyperbolic cosine of x. 84 85 degrees(...) 86 degrees(x) 87 88 Convert angle x from radians to degrees. 89 90 erf(...) 91 erf(x) 92 93 Error function at x. 94 95 erfc(...) 96 erfc(x) 97 98 Complementary error function at x. 99 100 exp(...) 101 exp(x) 102 103 Return e raised to the power of x. 104 105 expm1(...) 106 expm1(x) 107 108 Return exp(x)-1. 109 This function avoids the loss of precision involved in the direct evaluation of exp(x)-1 for small x. 110 111 fabs(...) 112 fabs(x) 113 114 Return the absolute value of the float x. 115 116 factorial(...) 117 factorial(x) -> Integral 118 119 Find x!. Raise a ValueError if x is negative or non-integral. 120 121 floor(...) 122 floor(x) 123 124 Return the floor of x as an Integral. 125 This is the largest integer <= x. 126 127 fmod(...) 128 fmod(x, y) 129 130 Return fmod(x, y), according to platform C. x % y may differ. 131 132 frexp(...) 133 frexp(x) 134 135 Return the mantissa and exponent of x, as pair (m, e). 136 m is a float and e is an int, such that x = m * 2.**e. 137 If x is 0, m and e are both 0. Else 0.5 <= abs(m) < 1.0. 138 139 fsum(...) 140 fsum(iterable) 141 142 Return an accurate floating point sum of values in the iterable. 143 Assumes IEEE-754 floating point arithmetic. 144 145 gamma(...) 146 gamma(x) 147 148 Gamma function at x. 149 150 gcd(...) 151 gcd(x, y) -> int 152 greatest common divisor of x and y 153 154 hypot(...) 155 hypot(x, y) 156 157 Return the Euclidean distance, sqrt(x*x + y*y). 158 159 isclose(...) 160 isclose(a, b, *, rel_tol=1e-09, abs_tol=0.0) -> bool 161 162 Determine whether two floating point numbers are close in value. 163 164 rel_tol 165 maximum difference for being considered "close", relative to the 166 magnitude of the input values 167 abs_tol 168 maximum difference for being considered "close", regardless of the 169 magnitude of the input values 170 171 Return True if a is close in value to b, and False otherwise. 172 173 For the values to be considered close, the difference between them 174 must be smaller than at least one of the tolerances. 175 176 -inf, inf and NaN behave similarly to the IEEE 754 Standard. That 177 is, NaN is not close to anything, even itself. inf and -inf are 178 only close to themselves. 179 180 isfinite(...) 181 isfinite(x) -> bool 182 183 Return True if x is neither an infinity nor a NaN, and False otherwise. 184 185 isinf(...) 186 isinf(x) -> bool 187 188 Return True if x is a positive or negative infinity, and False otherwise. 189 190 isnan(...) 191 isnan(x) -> bool 192 193 Return True if x is a NaN (not a number), and False otherwise. 194 195 ldexp(...) 196 ldexp(x, i) 197 198 Return x * (2**i). 199 200 lgamma(...) 201 lgamma(x) 202 203 Natural logarithm of absolute value of Gamma function at x. 204 205 log(...) 206 log(x[, base]) 207 208 Return the logarithm of x to the given base. 209 If the base not specified, returns the natural logarithm (base e) of x. 210 211 log10(...) 212 log10(x) 213 214 Return the base 10 logarithm of x. 215 216 log1p(...) 217 log1p(x) 218 219 Return the natural logarithm of 1+x (base e). 220 The result is computed in a way which is accurate for x near zero. 221 222 log2(...) 223 log2(x) 224 225 Return the base 2 logarithm of x. 226 227 modf(...) 228 modf(x) 229 230 Return the fractional and integer parts of x. Both results carry the sign 231 of x and are floats. 232 233 pow(...) 234 pow(x, y) 235 236 Return x**y (x to the power of y). 237 238 radians(...) 239 radians(x) 240 241 Convert angle x from degrees to radians. 242 243 sin(...) 244 sin(x) 245 246 Return the sine of x (measured in radians). 247 248 sinh(...) 249 sinh(x) 250 251 Return the hyperbolic sine of x. 252 253 sqrt(...) 254 sqrt(x) 255 256 Return the square root of x. 257 258 tan(...) 259 tan(x) 260 261 Return the tangent of x (measured in radians). 262 263 tanh(...) 264 tanh(x) 265 266 Return the hyperbolic tangent of x. 267 268 trunc(...) 269 trunc(x:Real) -> Integral 270 271 Truncates x to the nearest Integral toward 0. Uses the __trunc__ magic method. 272 273 DATA 274 e = 2.718281828459045 275 inf = inf 276 nan = nan 277 pi = 3.141592653589793 278 279 FILE 280 (built-in) 281 282 283 >>>
常用内置函数及其功能简要说明如表1.3.2.3所示，其中方括号内的参数可以忽略
| 函数 | 功能简要说明 |
| abs(x) | 返回数字 x 的绝对值或复数的模 |
| all(iterable) | 如果对于可迭代对象iterable中所有元素 x 都有 bool(x) 为 True，则返回 True。对于空的可迭代对象也返回 True |
| any(iterable) | 只要可迭代iterable中存在元素x使得bool(x)为True，则返回True。对于空的可迭代对象返回False |
| bin(x) | 将数字x转换为二进制 |
| bool(x) | 返回与x等价的布尔值 True 或 False |
| callable(object) | 测试对象object是否可调用，类和函数是可调用的，包含__call__()方法的类的对象也是可调用的 |
| compile() | 用于把Python代码编译成可被 exec() 或 eval() 函数执行的代码对象 |
| chr(x) | 返回Unicode编码为x的字符 |
| dir(obj) | 返回指定对象obj或模块obj的成员列表 |
| eval(s[,globals[,locals]]) | 计算并返回字符串 s 中表达式的值 |
| exec(x) | 执行代码或代码对象 x |
| filter(func,seq) | 返回filter对象，其中包含序列seq中使得单参数函数func返回值为True的那些元素，如果函数func为None则返回那些值等价于True的元素 |
| float(x) | 把数字或字符串x转换为浮点数并返回 |
| hasattr(obj,name) | 测试对象obj是否具有成员name |
| hash(x) | 返回对象 x 的哈希值，如果 x 不可哈希则抛出异常 |
| help(obj) | 返回对象obj的帮助信息 |
| hex(x) | 把数字x转换为十六进制 |
| id(obj) | 返回对象obj的帮助信息 |
| input([提示内容字符串]) | 接收键盘输入的内容，返回字符串 |
| int(x[,d]) | 返回数字x的整数部分，或把d进制的字符串转换为十进制并返回，d默认为十进制 |
| isinstance(object,class-or-type-or-tuple) | 测试对象object是否属于指定类型（如果有多个类型的话需要放到tuple中）的实例 |
| len(obj) | 返回对象obj包含的元素个数，适用于列表、元组、集合、字典、字符串、range对象和其他可迭代类型的对象 |
| list([x])、set([x])、tuple([x])、dict([x]) | 把对象x转换为列表、集合、元组、或字典并返回，或生成空列表、空集合、空元组、空字典 |
| map(func,seq) | 将函数func映射至序列seq中每个元素，返回包含函数值的map对象 |
| max(x)、min(x) | 返回序列x中的最大值、最小值，要求序列x中的所有元素之间可比较大小 |
| next(x) | 返回可迭代对象x中的下一个元素 |
| sum(x) | 返回序列x中所有元素之和，要求序列x中的所有元素必须为数字 |
| oct(x) | 把数字x转换为八进制 |
| open(name[,mode]) | 以指定模式mode打开文件name并返回文件对象 |
| ord(x) | 返回一个字符x的Unicode编码 |
| pow(x,y) | 返回x的y次方，等价于x **y |
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print(value,...,sep=\'\',end=\'\\n\',file= sys.stdout,flush=False) |
基本输出函数 |
| 21个常用代码片段 |