函数
| Built-in Functions | ||||
|---|---|---|---|---|
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() Return True if all elements of the iterable are 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 True
any() Return True if any element of the iterable is true. If the iterable is empty, return False. 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 False
ascii() Return a string containing a printable representation of an object, but escape the non-ASCII characters in the string returned by using \x, \u or \U escapes. 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. If x is not a Python object, it has to define an 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'
bool() Return a Boolean value, i.e. one of True or False. x is converted using the standard . If x is false or omitted, this returns False; otherwise it returns True. The class is a subclass of (see ). It cannot be subclassed further. Its only instances are False and True (see ).返回一个布尔值 。
bytearray() Return a new array of bytes. The class is a mutable sequence of integers in the range 0 <= x < 256. It has most of the usual methods of mutable sequences, described in , as well as most methods that the type has, see .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 the object argument is an instance of the classinfo argument, or of a (direct, indirect or ) subclass thereof. If object is not an object of the given type, the function always returns false. If classinfo is a tuple of type objects (or recursively, other such tuples), return true if object is an instance of any of the types. If classinfo is not a type or tuple of types and such tuples, a exception 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 -x 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, ny
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 s