python基础之数据类型与变量
一.变量
变量
声明变量
#!/usr/bin/env python
age=18
gender1='male'
gender2='female'
变量作用：保存状态（程序的运行本质是一系列状态的变化，变量的目的就是用来保存状态，变量值的变化就构成了程序运行的不同结果。）
例如：CS枪战，一个人的生命可以表示为life＝active表示存活，当满足某种条件后修改变量life＝inactive表示死亡。- 变量命名规则遵循标识符命名规则，详见第二篇
- name＝'lhf':'lhf'才是内存变量，name只是内存变量的引用
- 与c的区别在于变量赋值操作无返回值
- 链式赋值：y＝x＝a＝1
- 多元赋值：x,y=1,2 x,y=y,x
- 增量赋值：x+=1
二.数据类型
2.1 什么是数据类型及数据类型分类
程序的本质就是驱使计算机去处理各种状态的变化，这些状态分为很多种
例如英雄联盟游戏，一个人物角色有名字，钱，等级，装备等特性，大家第一时间会想到这么表示
名字：德玛西亚－－－－－－－－－－－－>字符串
钱：10000 －－－－－－－－－－－－>数字
等级：15 －－－－－－－－－－－－>数字
装备：鞋子，日炎斗篷，兰顿之兆－－－－>列表
(记录这些人物特性的是变量，这些特性的真实存在则是变量的值，存不同的特性需要用不同类型的值)
python中的数据类型
python使用对象模型来存储数据，每一个数据类型都有一个内置的类，每新建一个数据，实际就是在初始化生成一个对象，即所有数据都是对象
对象三个特性- 身份：内存地址，可以用id()获取
- 类型：决定了该对象可以保存什么类型值，可执行何种操作，需遵循什么规则，可用type()获取
- 值：对象保存的真实数据
注：在定义数据类型时，只需这样：x＝1，内部生成1这一内存对象会自动触发，我们无需关心。
这里的字符串、数字、列表等都是数据类型（用来描述某种状态或者特性）除此之外还有很多其他数据，处理不同的数据就需要定义不同的数据类型标准类型 | 其他类型 |
数字 | 类型type |
字符串 | Null |
列表 | 文件 |
元组 | 集合 |
字典 | 函数／方法 |
| 类 |
| 模块 |
2.2 标准数据类型：
2.2.1 数字
定义：a＝1
特性：
1.只能存放一个值
2.一经定义，不可更改
3.直接访问
分类：整型，长整型，布尔，浮点，复数
2.2.1.1 整型:
Python的整型相当于C中的long型,Python中的整数可以用十进制,八进制,十六进制表示。
>>> 10
10 --------->默认十进制
>>> oct(10)
'012' --------->八进制表示整数时，数值前面要加上一个前缀“0”
>>> hex(10)
'0xa' --------->十六进制表示整数时，数字前面要加上前缀0X或0x
python2.*与python3.*关于整型的区别
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，即-2147483648～2147483647
在64位系统上，整数的位数为64位，取值范围为-2**63～2**63-1，即-9223372036854775808～9223372036854775807
python3.*整形长度无限制
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
class int(object):
"""
int(x=0) -> integer
int(x, base=10) -> integer
Convert a number or string to an integer, or return 0 if no arguments
are given. If x is a number, return x.__int__(). For floating point
numbers, this truncates towards zero.
If x is not a number or if base is given, then x must be a string,
bytes, or bytearray instance 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)
4
"""
def bit_length(self): # real signature unknown; restored from __doc__
""" 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()
6
"""
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
@classmethod # known case
def from_bytes(cls, bytes, byteorder, *args, **kwargs): # real signature unknown; NOTE: unreliably restored from __doc__
"""
int.from_bytes(bytes, byteorder, *, signed=False) -> int
Return the integer represented by the given array of bytes.
The bytes argument must be a bytes-like object (e.g. bytes or bytearray).
The byteorder argument determines the byte order used to represent the
integer. If byteorder is 'big', the most significant byte is at the
beginning of the byte array. If byteorder is 'little', the most
significant byte is at the end of the byte array. To request the native
byte order of the host system, use `sys.byteorder' as the byte order value.
The signed keyword-only argument indicates whether two's complement is
used to represent the integer.
"""
pass
def to_bytes(self, length, byteorder, *args, **kwargs): # real signature unknown; NOTE: unreliably restored from __doc__
"""
int.to_bytes(length, byteorder, *, signed=False) -> bytes
Return an array of bytes representing an integer.
The integer is represented using length bytes. An OverflowError is
raised if the integer is not representable with the given number of
bytes.
The byteorder argument determines the byte order used to represent the
integer. If byteorder is 'big', the most significant byte is at the
beginning of the byte array. If byteorder is 'little', the most
significant byte is at the end of the byte array. To request the native
byte order of the host system, use `sys.byteorder' as the byte order value.
The signed keyword-only argument determines whether two's complement is
used to represent the integer. If signed is False and a negative integer
is given, an OverflowError is raised.
"""
pass
def __abs__(self, *args, **kwargs): # real signature unknown
""" abs(self) """
pass
def __add__(self, *args, **kwargs): # real signature unknown
""" Return self+value. """
pass
def __and__(self, *args, **kwargs): # real signature unknown
""" Return self&value. """
pass
def __bool__(self, *args, **kwargs): # real signature unknown
""" self != 0 """
pass
def __ceil__(self, *args, **kwargs): # real signature unknown
"""
整数返回自己
如果是小数
math.ceil(3.1)返回4
"""
""" Ceiling of an Integral returns itself. """
pass
def __divmod__(self, *args, **kwargs): # real signature unknown
""" 相除，得到商和余数组成的元组 """
""" Return divmod(self, value). """
pass
def __eq__(self, *args, **kwargs): # real signature unknown
""" Return self==value. """
pass
def __float__(self, *args, **kwargs): # real signature unknown
""" float(self) """
pass
def __floordiv__(self, *args, **kwargs): # real signature unknown
""" Return self//value. """
pass
def __floor__(self, *args, **kwargs): # real signature unknown
""" Flooring an Integral returns itself. """
pass
def __format__(self, *args, **kwargs): # real signature unknown
pass
def __getattribute__(self, *args, **kwargs): # real signature unknown
""" Return getattr(self, name). """
pass
def __getnewargs__(self, *args, **kwargs): # real signature unknown
pass
def __ge__(self, *args, **kwargs): # real signature unknown
""" Return self>=value. """
pass
def __gt__(self, *args, **kwargs): # real signature unknown
""" Return self>value. """
pass
def __hash__(self, *args, **kwargs): # real signature unknown
""" Return hash(self). """
pass
def __index__(self, *args, **kwargs): # real signature unknown
""" 用于切片，数字无意义 """
""" Return self converted to an integer, if self is suitable for use as an index into a list. """
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) -> integer
int(x, base=10) -> integer
Convert a number or string to an integer, or return 0 if no arguments
are given. If x is a number, return x.__int__(). For floating point
numbers, this truncates towards zero.
If x is not a number or if base is given, then x must be a string,
bytes, or bytearray instance 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)
4
# (copied from class doc)
"""
pass
def __int__(self, *args, **kwargs): # real signature unknown
""" int(self) """
pass
def __invert__(self, *args, **kwargs): # real signature unknown
""" ~self """
pass
def __le__(self, *args, **kwargs): # real signature unknown
""" Return self<=value. """
pass
def __lshift__(self, *args, **kwargs): # real signature unknown
""" Return self<<value. """
pass
def __lt__(self, *args, **kwargs): # real signature unknown
""" Return self<value. """
pass
def __mod__(self, *args, **kwargs): # real signature unknown
""" Return self%value. """
pass
def __mul__(self, *args, **kwargs): # real signature unknown
""" Return self*value. """
pass
def __neg__(self, *args, **kwargs): # real signature unknown
""" -self """
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 __ne__(self, *args, **kwargs): # real signature unknown
""" Return self!=value. """
pass
def __or__(self, *args, **kwargs): # real signature unknown
""" Return self|value. """
pass
def __pos__(self, *args, **kwargs): # real signature unknown
""" +self """
pass
def __pow__(self, *args, **kwargs): # real signature unknown
""" Return pow(self, value, mod). """
pass
def __radd__(self, *args, **kwargs): # real signature unknown
""" Return value+self. """
pass
def __rand__(self, *args, **kwargs): # real signature unknown
""" Return value&self. """
pass
def __rdivmod__(self, *args, **kwargs): # real signature unknown
""" Return divmod(value, self). """
pass
def __repr__(self, *args, **kwargs): # real signature unknown
""" Return repr(self). """
pass
def __rfloordiv__(self, *args, **kwargs): # real signature unknown
""" Return value//self. """
pass
def __rlshift__(self, *args, **kwargs): # real signature unknown
""" Return value<<self. """
pass
def __rmod__(self, *args, **kwargs): # real signature unknown
""" Return value%self. """
pass
def __rmul__(self, *args, **kwargs): # real signature unknown
""" Return value*self. """
pass
def __ror__(self, *args, **kwargs): # real signature unknown
""" Return value|self. """
pass
def __round__(self, *args, **kwargs): # real signature unknown
"""
Rounding an Integral returns itself.
Rounding with an ndigits argument also returns an integer.
"""
pass
def __rpow__(self, *args, **kwargs): # real signature unknown
""" Return pow(value, self, mod). """
pass
def __rrshift__(self, *args, **kwargs): # real signature unknown
""" Return value>>self. """
pass
def __rshift__(self, *args, **kwargs): # real signature unknown
""" Return self>>value. """
pass
def __rsub__(self, *args, **kwargs): # real signature unknown
""" Return value-self. """
pass
def __rtruediv__(self, *args, **kwargs): # real signature unknown
""" Return value/self. """
pass
def __rxor__(self, *args, **kwargs): # real signature unknown
""" Return value^self. """
pass
def __sizeof__(self, *args, **kwargs): # real signature unknown
""" Returns size in memory, in bytes """
pass
def __str__(self, *args, **kwargs): # real signature unknown
""" Return str(self). """
pass
def __sub__(self, *args, **kwargs): # real signature unknown
""" Return self-value. """
pass
def __truediv__(self, *args, **kwargs): # real signature unknown
""" Return self/value. """
pass
def __trunc__(self, *args, **kwargs): # real signature unknown
""" Truncating an Integral returns itself. """
pass
def __xor__(self, *args, **kwargs): # real signature unknown
""" Return self^value. """
pass
denominator = property(lambda self: object(), lambda self, v: None, lambda self: None) # default
"""the denominator of a rational number in lowest terms"""
imag = property(lambda self: object(), lambda self, v: None, lambda self: None) # default
"""the imaginary part of a complex number"""
numerator = property(lambda self: object(), lambda self, v: None, lambda self: None) # default
"""the numerator of a rational number in lowest terms"""
real = property(lambda self: object(), lambda self, v: None, lambda self: None) # default
"""the real part of a complex number"""
2.2.1.2 长整型long：
python2.*：
跟C语言不同，Python的长整型没有指定位宽，也就是说Python没有限制长整型数值的大小，
但是实际上由于机器内存有限，所以我们使用的长整型数值不可能无限大。
在使用过程中，我们如何区分长整型和整型数值呢？
通常的做法是在数字尾部加上一个大写字母L或小写字母l以表示该整数是长整型的，例如：
a = 9223372036854775808L
注意，自从Python2起，如果发生溢出，Python会自动将整型数据转换为长整型，
所以如今在长整型数据后面不加字母L也不会导致严重后果了。
python3.*
长整型，整型统一归为整型
python2.7
>>> a=9223372036854775807
>>> a
9223372036854775807
>>> a+=1
>>> a
9223372036854775808L
python3.5
>>> a=9223372036854775807
>>> a
9223372036854775807
>>> a+=1
>>> a
9223372036854775808
2.2.1.3 布尔bool:
True 和False
1和02.2.1.4 浮点数float:
Python的浮点数就是数学中的小数，类似C语言中的double。
在运算中，整数与浮点数运算的结果是浮点数
浮点数也就是小数，之所以称为浮点数，是因为按照科学记数法表示时，
一个浮点数的小数点位置是可变的，比如，1.23*109和12.3*108是相等的。
浮点数可以用数学写法，如1.23，3.14，-9.01，等等。但是对于很大或很小的浮点数，
就必须用科学计数法表示，把10用e替代，1.23*109就是1.23e9，或者12.3e8，0.000012
可以写成1.2e-5，等等。
整数和浮点数在计算机内部存储的方式是不同的，整数运算永远是精确的而浮点数运算则可能会有
四舍五入的误差。2.2.1.5 复数complex:
复数由实数部分和虚数部分组成，一般形式为x＋yj，其中的x是复数的实数部分，y是复数的虚数部分，这里的x和y都是实数。
注意，虚数部分的字母j大小写都可以，
>>> 1.3 + 2.5j == 1.3 + 2.5J
True
2.2.1.6 数字相关内建函数
2.2.2 字符串
定义：它是一个有序的字符的集合，用于存储和表示基本的文本信息，‘’或“”或‘’‘ ’‘’中间包含的内容称之为字符串
特性：
1.只能存放一个值
2.不可变
3.按照从左到右的顺序定义字符集合，下标从0开始顺序访问，有序
补充：
1.字符串的单引号和双引号都无法取消特殊字符的含义，如果想让引号内所有字符均取消特殊意义，在引号前面加r，如name＝r'l\thf'
2.unicode字符串与r连用必需在r前面，如name＝ur'l\thf'2.2.2.1 字符串创建
‘hello world’
2.2.2.2 字符串常用操作
移除空白 x.strip()
分割 x.split('/')
长度 len(x)
索引 x[3] 或者x[-1]
切片 x[0:5:2] #0 2 4
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