python基本数据类型——int

一、int的范围

python2：

　　在32位机器上，整数的位数为32位，取值范围为-2**31～2**31-1；
　　在64位系统上，整数的位数为64位，取值范围为-2**63～2**63-1；

python3：

　　理论上长度是无限的（只要内存足够大）

二、python内存机制

在一般情况下当变量被赋值后，内存和变量的关系如下：

特殊情况：

python内的优化机制（不论是2.7还是3.5都有）：

-5 ~ 257 之间的数，如果使用第一种赋值方式，那么他们依然属于同一块内存（可以用id查看）

三、源码

 class int(object):
     """
     int(x=0) -> int or long
     int(x, base=10) -> int or long

     Convert a number or string to an integer, or return 0 if no arguments
     are given.  If x is floating point, the conversion truncates towards zero.
     If x is outside the integer range, the function returns a long instead.

     If x is not a number or if base is given, then x must be a string or
     Unicode object representing an integer literal in the given base.  The
     literal can be preceded by '+' or '-' and be surrounded by whitespace.
     The base defaults to 10.  Valid bases are 0 and 2-36.  Base 0 means to
     interpret the base from the string as an integer literal.
     >>> int('0b100', base=0)
     """
     def bit_length(self):
         """ 返回表示该数字的时占用的最少位数 """
         """
         int.bit_length() -> int

         Number of bits necessary to represent self in binary.
         >>> bin(37)
         '0b100101'
         >>> (37).bit_length()
         """
         return 0

     def conjugate(self, *args, **kwargs): # real signature unknown
         """ 返回该复数的共轭复数 """
         """ Returns self, the complex conjugate of any int. """
         pass

     def __abs__(self):
         """ 返回绝对值 """
         """ x.__abs__() <==> abs(x) """
         pass

     def __add__(self, y):
         """ x.__add__(y) <==> x+y """
         pass

     def __and__(self, y):
         """ x.__and__(y) <==> x&y """
         pass

     def __cmp__(self, y):
         """ 比较两个数大小 """
         """ x.__cmp__(y) <==> cmp(x,y) """
         pass

     def __coerce__(self, y):
         """ 强制生成一个元组 """
         """ x.__coerce__(y) <==> coerce(x, y) """
         pass

     def __divmod__(self, y):
         """ 相除，得到商和余数组成的元组 """
         """ x.__divmod__(y) <==> divmod(x, y) """
         pass

     def __div__(self, y):
         """ x.__div__(y) <==> x/y """
         pass

     def __float__(self):
         """ 转换为浮点类型 """
         """ x.__float__() <==> float(x) """
         pass

     def __floordiv__(self, y):
         """ x.__floordiv__(y) <==> x//y """
         pass

     def __format__(self, *args, **kwargs): # real signature unknown
         pass

     def __getattribute__(self, name):
         """ x.__getattribute__('name') <==> x.name """
         pass

     def __getnewargs__(self, *args, **kwargs): # real signature unknown
         """ 内部调用 __new__方法或创建对象时传入参数使用 """
         pass

     def __hash__(self):
         """如果对象object为哈希表类型，返回对象object的哈希值。哈希值为整数。在字典查找中，哈希值用于快速比较字典的键。两个数值如果相等，则哈希值也相等。"""
         """ x.__hash__() <==> hash(x) """
         pass

     def __hex__(self):
         """ 返回当前数的 十六进制 表示 """
         """ x.__hex__() <==> hex(x) """
         pass

     def __index__(self):
         """ 用于切片，数字无意义 """
         """ x[y:z] <==> x[y.__index__():z.__index__()] """
         pass

     def __init__(self, x, base=10): # known special case of int.__init__
         """ 构造方法，执行 x = 123 或 x = int(10) 时，自动调用，暂时忽略 """
         """
         int(x=0) -> int or long
         int(x, base=10) -> int or long

         Convert a number or string to an integer, or return 0 if no arguments
         are given.  If x is floating point, the conversion truncates towards zero.
         If x is outside the integer range, the function returns a long instead.

         If x is not a number or if base is given, then x must be a string or
         Unicode object representing an integer literal in the given base.  The
         literal can be preceded by '+' or '-' and be surrounded by whitespace.
         The base defaults to 10.  Valid bases are 0 and 2-36.  Base 0 means to
         interpret the base from the string as an integer literal.
         >>> int('0b100', base=0)
         # (copied from class doc)
         """
         pass

     def __int__(self):
         """ 转换为整数 """
         """ x.__int__() <==> int(x) """
         pass

     def __invert__(self):
         """ x.__invert__() <==> ~x """
         pass

     def __long__(self):
         """ 转换为长整数 """
         """ x.__long__() <==> long(x) """
         pass

     def __lshift__(self, y):
         """ x.__lshift__(y) <==> x<<y """
         pass

     def __mod__(self, y):
         """ x.__mod__(y) <==> x%y """
         pass

     def __mul__(self, y):
         """ x.__mul__(y) <==> x*y """
         pass

     def __neg__(self):
         """ x.__neg__() <==> -x """
         pass

     @staticmethod # known case of __new__
     def __new__(S, *more):
         """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
         pass

     def __nonzero__(self):
         """ x.__nonzero__() <==> x != 0 """
         pass

     def __oct__(self):
         """ 返回改值的 八进制 表示 """
         """ x.__oct__() <==> oct(x) """
         pass

     def __or__(self, y):
         """ x.__or__(y) <==> x|y """
         pass

     def __pos__(self):
         """ x.__pos__() <==> +x """
         pass

     def __pow__(self, y, z=None):
         """ 幂，次方 """
         """ x.__pow__(y[, z]) <==> pow(x, y[, z]) """
         pass

     def __radd__(self, y):
         """ x.__radd__(y) <==> y+x """
         pass

     def __rand__(self, y):
         """ x.__rand__(y) <==> y&x """
         pass

     def __rdivmod__(self, y):
         """ x.__rdivmod__(y) <==> divmod(y, x) """
         pass

     def __rdiv__(self, y):
         """ x.__rdiv__(y) <==> y/x """
         pass

     def __repr__(self):
         """转化为解释器可读取的形式 """
         """ x.__repr__() <==> repr(x) """
         pass

     def __str__(self):
         """转换为人阅读的形式，如果没有适于人阅读的解释形式的话，则返回解释器课阅读的形式"""
         """ x.__str__() <==> str(x) """
         pass

     def __rfloordiv__(self, y):
         """ x.__rfloordiv__(y) <==> y//x """
         pass

     def __rlshift__(self, y):
         """ x.__rlshift__(y) <==> y<<x """
         pass

     def __rmod__(self, y):
         """ x.__rmod__(y) <==> y%x """
         pass

     def __rmul__(self, y):
         """ x.__rmul__(y) <==> y*x """
         pass

     def __ror__(self, y):
         """ x.__ror__(y) <==> y|x """
         pass

     def __rpow__(self, x, z=None):
         """ y.__rpow__(x[, z]) <==> pow(x, y[, z]) """
         pass

     def __rrshift__(self, y):
         """ x.__rrshift__(y) <==> y>>x """
         pass

     def __rshift__(self, y):
         """ x.__rshift__(y) <==> x>>y """
         pass

     def __rsub__(self, y):
         """ x.__rsub__(y) <==> y-x """
         pass

     def __rtruediv__(self, y):
         """ x.__rtruediv__(y) <==> y/x """
         pass

     def __rxor__(self, y):
         """ x.__rxor__(y) <==> y^x """
         pass

     def __sub__(self, y):
         """ x.__sub__(y) <==> x-y """
         pass

     def __truediv__(self, y):
         """ x.__truediv__(y) <==> x/y """
         pass

     def __trunc__(self, *args, **kwargs):
         """ 返回数值被截取为整形的值，在整形中无意义 """
         pass

     def __xor__(self, y):
         """ x.__xor__(y) <==> x^y """
         pass

     denominator = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """ 分母 = 1 """
     """the denominator of a rational number in lowest terms"""

     imag = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """ 虚数，无意义 """
     """the imaginary part of a complex number"""

     numerator = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """ 分子 = 数字大小 """
     """the numerator of a rational number in lowest terms"""

     real = property(lambda self: object(), lambda self, v: None, lambda self: None)  # default
     """ 实属，无意义 """
     """the real part of a complex number"""

 int

int

小知识点：

在python2中：

test = 9 / 2
输出—— 4

from __future__ import division
test = 9 / 2
输出—— 4.5

而在python3中：

test = 9 / 2
输出—— 4.5