Python numeric types introduced

Data Type Description

• Python data types can be divided into: numeric and non-numeric type
• Numeric
  • Integer (int)
  • Float (float)
  • Boolean (bool)
    • True (True)
    • False (False)
  • Complex type (complex)
    • Mainly used for scientific computing
• Non-digital type
  • String (str)
  • List (list)
  • Tuple (tuple)
  • Dictionary (dict)
• In Python, all non-numeric type variable, have a common characteristic:
  • It is a sequence that can be understood as a container

Digital Type

　　On 32-bit machines, the number of bits for 32-bit integer in the range of -2 31 to 2 31 - 1 ~ -2147483648 2147483647 i.e.

　　In the 64-bit system, 64 bits for an integer in the range of -2 63 to 2 63-1 ~ 9223372036854775807 i.e. -9223372036854775808

Type of digital creation

#!/usr/bin/env python3
# -*-coding:utf-8-*-

"""
@author:fyh
@time:2019/5/31
"""
# int类型创建
a = 10
b = 666

print(a)  # 10
print(b)  # 666
print(type(a))  # <class 'int'>

# float类型创建
c = 3.14
print(c)
print(type(c))  # <class 'float'>

# complex类型创建
d = 3 + 4j
print(d)
print(type(d))  # <class 'complex'>

# 布尔型
flag = True
print(flag)
print(type(flag))   # <class 'bool'>

type (obj) function can view the type of variable

Data type conversion

Sometimes, we need to built-in data type conversion, data type conversion, you only need to type the data as a function name.

• int (x) will be converted to an integer x
• a float (x) to convert to a floating-point number x
• Complex (x) will be converted to a complex number x, x is a real part, imaginary part is 0
• Complex (x, y) x and y to convert a complex number, x is the real part, imaginary part to y. x and y are numeric expression
• bool (x) will be converted to type bool x, it is non-zero True, False 0

#!/usr/bin/env python3
# -*-coding:utf-8-*-

"""
@author:fyh
@time:2019/5/31
"""

# int(x)
var1 = 3.14
print(int(var1))  # 3

# float(x)
var2 = 3
print(float(var2))  # 3.0

# complex(x)
var3 = 4
var4 = 2
print(complex(var3))    # (4+0j)
# complex(x, y)
print(complex(var3, var4))  # (4+2j)

# bool(x)
var5 = 1
print(bool(var5))   # True
var6 = 0
print(bool(var6))   # False

When numeric type conversion, x is the only type of digital conversion, if other types will complain:

str1 = "a"
print(int(str1))　　# 会报错

computation

#!/usr/bin/env python3
# -*-coding:utf-8-*-

"""
@author:fyh
@time:2019/5/31
"""

print(2 + 2)    # 4

print(50 - 5*5)     # 25

print(8 / 5)    # 1.6
# 在整数除法中，除法 / 总是返回一个浮点数，如果只想得到整数的结果，丢弃可能的分数部分，可以使用运算符 //
print(17 / 3)   # 5.666666666666667

print(17 // 3)  # 5

# 注意：// 得到的并不一定是整数类型的数，它与分母分子的数据类型有关系。
print(7.0 // 2)     # 3.0
print(7 // 2.0)     # 3.0

# ％操作符返回除法的余数
print(17 % 3)   # 2

# Python 可以使用 ** 操作来进行幂运算
print(5 ** 2)   # 25
print(2 ** 7)   # 128

Digital type related functions

Math-related functions in the math package

# abs(x) 返回数字的绝对值，如abs(-10) 返回 10
# ceil(x) 返回数字的上入整数，如math.ceil(4.1) 返回 5
# cmp(x, y) 如果 x < y 返回 -1, 如果 x == y 返回 0, 如果 x > y 返回 1
# exp(x) 返回e的x次幂(ex),如math.exp(1) 返回2.718281828459045
# fabs(x) 返回数字的绝对值，如math.fabs(-10) 返回10.0
# floor(x) 返回数字的下舍整数，如math.floor(4.9)返回 4
# log(x) 如math.log(math.e)返回1.0,math.log(100,10)返回2.0
# log10(x) 返回以10为基数的x的对数，如math.log10(100)返回 2.0
# max(x1, x2,...) 返回给定参数的最大值，参数可以为序列。
# min(x1, x2,...) 返回给定参数的最小值，参数可以为序列。
# modf(x) 返回x的整数部分与小数部分，两部分的数值符号与x相同，整数部分以浮点型表示。
# pow(x, y) x**y 运算后的值。
# round(x [,n]) 返回浮点数x的四舍五入值，如给出n值，则代表舍入到小数点后的位数。
# sqrt(x) 返回数字x的平方根，数字可以为负数，返回类型为实数，如math.sqrt(4)返回 2.0

Small integer object pool

>>> a = 5
>>> b = 5
>>> id(a),id(b)
(1892969616, 1892969616)
>>> c = 500
>>> d = 500
>>> id(c),id(d)
(2499230475376, 2499234158160)
>>>

Small integer object pooling: CPython integer from -5 to 256, there is a small integer objects in the pool forever, it will not be released.

Pooling: caching mechanism.