# /usr/bin/env python

# -*- coding: utf-8 -*-

# Date:2017/8/4 15:05

# __author__ = 'P0WER1ISA'

# __github__ = 'https://github.com/P0WER1ISA'

# 3.1 对数值进行取整 (使用内建函数round)

print(round(1.23, 1)) # 取整操作

print(round(4.42, 0))

print(round(3.1315, 3)) # 不要使用取整函数来进行“修正”精度，这里没有四舍五入。使用decimal模块

print(round(int(34.24))) # 转换int

x = 1.234567

print(format(x, '0.2f')) # 格式化操作

print(format(x, '0.3f')) # f:float 0.3=保留3位小数

# 3.2 执行精确的小数计算

a = 4.2

b = 2.1

print(a + b)

print((a + b) == 6.3) # False 误差由底层CPU的浮点运算单元和IEEE 754 浮点数算术标准的一种“特性”

from decimal import Decimal # 使用decimal的Decimal方法来进行小数计算

a = Decimal('4.2') # 数字以字符串形式录入

b = Decimal('2.1')

print(a + b)

print((a + b) == Decimal('6.3'))

from decimal import localcontext # 进行四舍五入

a = Decimal('1.3')

b = Decimal('1.7')

print(a / b)

with localcontext() as ctx: # localcontext 需要上下文环境，设置prec属性，保留小数位数

ctx.prec = 3

print(a / b)

# 3.3 对数值最格式化输出

x = 1234.56789

print(format(x, '0.2f')) # f:float 浮点数

print(format(x, '0.2e')) # e:科学计数

print(format(x, '>12.1f')) # >：靠右对齐，12：输出字符宽度，.1：保留一位小数，f：以float表示

print(format(x, '<8.1f')) # <：靠左对齐

print(format(x, '<8.1f')) # <：靠左对齐

print(format(x, ','))

print(format(x, '0,.1f'))

# 3.4 同二进制、八进制和十六进制数打交道

x = 1234

print(bin(x)) # 二进制，以'0b'开头

print(oct(x)) # 八进制，以'0o'开头

print(hex(x)) # 十六进制，以'0x'开头

print(format(x, 'b')) # 去掉'0b'的二进制

print(int('4d2', 16)) # 用int函数，将字符串形式的整数转换为不同的进制

print(int('10011010010', 2)) # 以2进制方式转换

# 3.5 从字节串中打包和解包大整数

data = b'\x00\x124V\x00x\x90\xab\x00\xcd\xef\x01\x00#\x004' # 16个元素的字节串

print(len(data))

print(int.from_bytes(data, 'little')) # 将字节转换为整型

print(int.from_bytes(data, 'big'))

x = 94522842520747284487117727783387188

print(x.to_bytes(16, 'big'))

print(x.to_bytes(16, 'little'))

# 3.6 复数运算 (复数是实属的延伸。实数是复数的真子集。实数=有理数+无理数。有理数=整数，0或分数。无理数=无限不循环小数)

a = complex(2, 4)

b = 3 - 5j

print(a)

print(b)

print(a.real) # 复数实部

print(b.imag) # 复数虚部

print(b.conjugate()) # 复数共轭值

import cmath

print(cmath.sin(a)) # 复数求正弦

print(cmath.cos(b)) # 复数求余弦

print(cmath.exp(a)) # 复数求平方根

# 3.7 处理无穷大和NaN

from numpy import inf # numpy模块中的inf，标识无穷数

import math

a = float(inf)

b = float(-inf)

c = float(inf * 0)

print(a is inf)

print(math.isinf(a)) # math模块中的isinf函数，判断是否是inf

print(math.isnan(b))

print(math.isnan(c))

# 分数的计算

from fractions import Fraction

a = Fraction(5, 4)

b = Fraction(7, 16)

print(a)

print(a + b)

c = a * b

print(c)

print(a.numerator)

print(a.denominator)

print(float(c))

# 3.9 处理大型数组的计算

x = [1, 2, 3, 4]

y = [4, 5, 6, 7]

print(x * 2)

import numpy as np

ax = np.array([4, 2, 5, 1])

ay = np.array([4, 5, 6, 7])

print(ax * 2)

print(ax + 10)

print(ax + ay)

print(ax * ay)

def f(x):

return 3 ** 2 - 2 * x + 7

print(f(ax))

print(np.sort(ax))

grid = np.zeros(shape=(10000, 10000), dtype=float)

print(grid + 10)

print(np.sinc(grid))

import numpy as np

a = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

print(a[1]) # select row 1

print(a[:, 1]) # select column 1

print(a[1:3, 1:2])

# 3.10 矩阵和线性代数的计算

import numpy as np

m = np.matrix([[1, -2, 3], [0, 4, 5], [7, 8, -9]])

print(m)

print(m.T)

print(m.I)

# 3.11 随机选择

import random

values = [1, 2, 3, 4, 5, 6, 7, 8]

random.shuffle(values) # 打乱序列顺序

print(values)

print(random.choice(values)) # 随机取出1个元素

print(random.sample(values, 2)) # 随机取出2个元素

print(random.randint(44, 244)) # 获得一个随机整数

# 3.2 时间换算

from datetime import timedelta # 计算时间间隔

a = timedelta(days=2, hours=6)

b = timedelta(hours=4.5)

c = a + b

print(c.days)

print(c.seconds)

print(c.total_seconds())

from datetime import datetime # 表示日期和时间

a = datetime(2017, 8, 6)

print(a + timedelta(days=10))

b = datetime(2018, 8, 6)

d = b - a

print(d.days)

now1 = datetime.today()

now2 = datetime.now()

print(now1 + timedelta(minutes=10))

print(now2)

# 计算上周5的日期

from datetime import datetime, timedelta

weekdays = ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday']

def get_previous_byday(dayname, start_date=None):

return target_date

print(datetime.today().weekday()) # datetime类的weekday()方法可以获得datetime是星期几,注意weekday() 返回的是0-6是星期一到星期日

print(weekdays.index('Sunday'))

print(get_previous_byday('Monday'))

print(get_previous_byday('Sunday'))

print(get_previous_byday('Sunday', datetime(2012, 12, 21)))

# 3.14 找出当月的日期范围

from datetime import datetime, date, timedelta

import calendar

def get_month_range(start_date=None):

return start_date, end_date

a_day = timedelta(days=1)

first_day, last_day = get_month_range()

while first_day < last_day:

print(first_day)

first_day += a_day

# 3.15 将字符串转换为日期

from datetime import datetime

text = '2012-9-02'

y = datetime.strptime(text, '%Y-%m-%d')

print(type(y), y)

print(datetime.strftime(datetime.now(), '%A %B %d, %Y')) # 将日期格式化

# 3.16 处理设计到时区的日期问题 (使用pzty模块)

from datetime import datetime

from pytz import timezone

d = datetime(2012, 12, 31, 9, 30, 0)

print(d)

central = timezone('US/Central') # 设置时区

loc_d = central.localize(d) # 时区当地时间

print(loc_d)