python入门（二），,函数Built-in
python入门（二），,函数Built-in
函数
| Built-in Functions | ||||
|---|---|---|---|---|
abs() | dict() | help() | min() | setattr() |
all() | dir() | hex() | next() | slice() |
any() | divmod() | id() | object() | sorted() |
ascii() | enumerate() | input() | oct() | staticmethod() |
bin() | eval() | int() | open() | str() |
bool() | exec() | isinstance() | ord() | sum() |
bytearray() | filter() | issubclass() | pow() | super() |
bytes() | float() | iter() | print() | tuple() |
callable() | format() | len() | property() | type() |
chr() | frozenset() | list() | range() | vars() |
classmethod() | getattr() | locals() | repr() | zip() |
compile() | globals() | map() | reversed() | __import__() |
complex() | hasattr() | max() | round() | |
delattr() | hash() | memoryview() | set() |
abs() Return the absolute value of a number. The argument may be an integer or a floating point number. If the argument is a complex number, its magnitude is returned.返回number类型的绝对值。参数应为整数或是浮点数。如果是复数，则取模∣z∣=√(a^2+b^2)
all() ReturnTrueif all elements of theiterableare true (or if the iterable is empty). Equivalent to:如果迭代对象中的所有元素都为true或迭代对象为空则返回true。空字符串，空列表，空元祖返回true。
def all(iterable): for element in iterable: if not element: return False return TrueView Code
any() ReturnTrueif any element of theiterableis true. If the iterable is empty, returnFalse. Equivalent to:迭代对象中任一元素为true，则返回true。迭代对象为空，返回false。
def any(iterable): for element in iterable: if element: return True return FalseView Code
ascii() Return a string containing a printable representation of an object, but escape the non-ASCII characters in the string returned byrepr()using\x,\uor\Uescapes. 返回一个对象的可打印的表示形式的字符串。如果不是ascII码，则返回\x,\u或\U的方式。
bin()Convert an integer number to a binary string prefixed with “0b”. The result is a valid Python expression. Ifxis not a Pythonintobject, it has to define an__index__()method that returns an integer. Some examples:将一个整型转化为带“0b”前缀的字符串。结果是一个有效的python表达式。如果参数不是Int类型，那么，他需要定义__index__()方法返回一个整数。
>>> bin(3)‘0b11‘>>> bin(-10)‘-0b1010‘View Code
bool()Return a Boolean value, i.e. one ofTrueorFalse.xis converted using the standardtruth testing procedure. Ifxis false or omitted, this returnsFalse; otherwise it returnsTrue. Theboolclass is a subclass ofint(seeNumeric Types — int, float, complex). It cannot be subclassed further. Its only instances areFalseandTrue(seeBoolean Values).返回一个布尔值 。
bytearray() Return a new array of bytes. Thebytearrayclass is a mutable sequence of integers in the range 0 <= x < 256. It has most of the usual methods of mutable sequences, described inMutable Sequence Types, as well as most methods that thebytestype has, seeBytes and Bytearray Operations.返回一个新的字节数组。字节数组是由0--256之间的数组成的可变序列。基本不理解，跳过。
isinstance() Return true if theobjectargument is an instance of theclassinfoargument, or of a (direct, indirect orvirtual) subclass thereof. Ifobjectis not an object of the given type, the function always returns false. Ifclassinfois a tuple of type objects (or recursively, other such tuples), return true ifobjectis an instance of any of the types. Ifclassinfois not a type or tuple of types and such tuples, aTypeErrorexception is raised.如果参数是某个数据类型的实例或子集则返回true。如果这种类型指的是元祖，只要检验的参数是任何一种类型的实例即返回true。
定义函数
在Python中，定义一个函数要使用def语句，依次写出函数名、括号、括号中的参数和冒号:，然后，在缩进块中编写函数体，函数的返回值用return语句返回。
空函数
def nop(): pass
参数检查
调用函数时，如果参数个数不对，Python解释器会自动检查出来，并抛出TypeError，参数类型不对无法检查。
def my_abs(x): if not isinstance(x, (int, float)): raise TypeError(‘bad operand type‘) if x >= 0: return x else: return -xView Code
返回多个值（返回一个tuple）
import mathdef move(x, y, step, angle=0): nx = x + step * math.cos(angle) ny = y - step * math.sin(angle) return nx, nyView Code
默认参数（必选参数在前，默认参数在后）
def power(x, n=2): s = 1 while n > 0: n = n - 1 s = s * x return sView Code
python入门（二）
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