【python程序设计】程序控制#181021-白红宇

【python程序设计】程序控制#181021

阅读量：7046 次

发布时间：2019-06-28

本文共 6609 字，大约阅读时间需要 22 分钟。

#!/usr/bin/env python3# -*- coding: UTF-8 -*-guess = eval(input())if guess == 99:    print("yes")====================== RESTART: C:\Python3.7.0\test.py ======================1>>> ====================== RESTART: C:\Python3.7.0\test.py ======================99yes#!/usr/bin/env python3# -*- coding: UTF-8 -*-guess = eval(input())print("猜{}了".format("对" if guess == 99 else "错"))====================== RESTART: C:\Python3.7.0\test.py ======================1猜错了>>> ====================== RESTART: C:\Python3.7.0\test.py ======================99猜对了

用于条件组合的三个保留字

x and y逻辑与x or y逻辑或not x逻辑非

异常处理

#!/usr/bin/env python3# -*- coding: UTF-8 -*-try:    num = eval(input("please input int num:"))    print(num ** 2)except:    print("not int")====================== RESTART: C:\Python3.7.0\test.py ======================please input int num:not int>>> ====================== RESTART: C:\Python3.7.0\test.py ======================please input int num:11121

#!/usr/bin/env python3# -*- coding: UTF-8 -*-try:    num = eval(input("please input int num:"))    print(num ** 2)except NameError:    print("not int")====================== RESTART: C:\Python3.7.0\test.py ======================please input int num:Traceback (most recent call last):  File "C:\Python3.7.0\test.py", line 5, in 
    
         num = eval(input("please input int num:"))  File "
     
      ", line 0        ^SyntaxError: unexpected EOF while parsing>>> ====================== RESTART: C:\Python3.7.0\test.py ======================please input int num:anot int

try:	
    <语句块1>
     except:	
     <语句块2>
      else:	
      <语句块3>
       finally:	
       <语句块4>
        - finally对应语句4一定执行- else对应语句块3在不发生异常时执行

身体质量指数BMI

BMI:Body Mass IndexBMI = 体重(kg) / 身高^2(m^2)分类	国际BMI值	国内BMI值偏瘦	<18.5		<18.5正常	18.5~25		18.5~24偏胖	25~30		24~28肥胖	>=30		>=28#!/usr/bin/env python3# -*- coding: UTF-8 -*-height,weight = eval(input("please input you height(m) and weight(kg)[,]:"))bmi = weight /pow(height,2)print("BMI is:{:.2f}".format(bmi))who,nat = "",""if bmi < 18.5:    who,nat = "偏瘦","偏瘦"elif 18.5 <= bmi < 24:    who,nat = "正常","正常"elif 24 <= bmi < 25:    who,nat = "正常","偏胖"elif 25 <= bmi <28:    who,nat = "偏胖","偏胖"elif 28 <= bmi < 30:    who,nat = "偏胖","肥胖"else:    who,nat = "肥胖","肥胖"print("BMI is:who'{0}',nat'{1}'".format(who,nat))====================== RESTART: C:\Python3.7.0\test.py ======================please input you height(m) and weight(kg)[,]:1.74,74BMI is:24.44BMI is:who'正常',nat'偏胖'

遍历循环

for i in range(M,N,K):	
    <语句块>
     range(起始值,终止值,步长)因为程序从0开始，终止值实际是-1字符串遍历>>> for i in "Python":	print(i,end=",")	P,y,t,h,o,n,列表遍历>>> for i in [123,"AAA",234]:	print(i,end=",")	123,AAA,234,文件遍历for line in fi:	
     <语句块>
      - fi是一个文件标识符，遍历其每行，产生循环

无限循环

while 
    <条件>
     :	
     <语句块>

循环控制保留字

break跳出并结束当前整个循环，执行循环后的语句（当前层）continue结束当次循环，继续执行后续次数循环#continuefor i in "python":    if i == "t":        continue    print(i,end="")>>> ====================== RESTART: C:\Python3.7.0\test.py ======================pyhon#breakfor i in "python":    if i == "t":        break    print(i,end="")====================== RESTART: C:\Python3.7.0\test.py ======================py

#!/usr/bin/env python3# -*- coding: UTF-8 -*-s = "123"while s != "":    for c in s:        print(c,end="")    s = s[:-1]====================== RESTART: C:\Python3.7.0\test.py ======================123121#!/usr/bin/env python3# -*- coding: UTF-8 -*-s = "python"while s != "":    for c in s:        if c == "t":            break        print(c,end="")    s = s[:-1]====================== RESTART: C:\Python3.7.0\test.py ======================pypypypypyp

循环高级用法

for 
    <循环变量>
      in 
     <遍历结构>
      :	
      <语句块1>
       else:	
       <语句块2>
        while <>:	
        <语句块1>
         else:	
         <语句块2>
          循环与else当循环没有被break语句退出时，执行else语句块else语句块作为正常完成循环的奖励这里else的用法与异常处理中else用法相似

#!/usr/bin/env python3# -*- coding: UTF-8 -*-for c in "python":    if c == "t":        continue    print(c,end="")else:    print("!")====================== RESTART: C:\Python3.7.0\test.py ======================pyhon!

#!/usr/bin/env python3# -*- coding: UTF-8 -*-for c in "python":    if c == "t":        break    print(c,end="")else:    print("!")====================== RESTART: C:\Python3.7.0\test.py ======================py

random库

伪随机数：采用梅森旋转算法生成的（伪）随机序列中元素基本随机数函数：seed(),random()扩展随机数函数：randint(),getrandbits(),uniform(),randrange(),choice(),shuffle()seed(a = None)初始化给定的随机数种子，默认当前系统时间>>> import random>>> random.seed(10)random()生成一个[0.0,1.0]之间的随机小数>>> random.random()0.5714025946899135

重复调用随机数相同>>> random.seed(10)>>> random.random()0.5714025946899135>>> random.seed(10)>>> random.random()0.5714025946899135

随机数刷新#!/usr/bin/env python3# -*- coding: UTF-8 -*-import randomimport timerandom.seed(10)while 1:    print("\r",random.random(),end="")    time.sleep(0.1)时间刷新#!/usr/bin/env python3# -*- coding: UTF-8 -*-import randomimport timet = time.gmtime()while 1:    t = time.gmtime()    print("\r",time.strftime("%Y-%m-%d %H:%M:%S",t),end="")    time.sleep(0.01)

扩展随机数函数

randint(a,b)生成一个[a,b]之间的整数>>> random.randint(5,10)9randrange(m,n,[k])生成一个[m,n]之间以k为步长的随机整数>>> random.randrange(50,100,2)76getrandbits(k)生成一个k比特长的随机整数>>> random.getrandbits(16)31625uniform(a,b)生成一个[a,b]之间的随机小数>>> random.uniform(5,10)7.890456505672352choice(seq)从序列seq中随机选择一个元素>>> random.choice([1,2,3,4,5,6,7,8,9])4shuffle(seq)将序列seq中元素随机排序，返回打乱后的序列>>> s = [1,2,3,4,5,6,7,8,9]>>> random.shuffle(s)>>> print(s)[6, 7, 5, 9, 4, 2, 8, 1, 3]

随机序列刷新#!/usr/bin/env python3# -*- coding: UTF-8 -*-import randomimport times = [1,2,3,4,5,6,7,8,9]while 1:    random.shuffle(s)    print("\r",s,end="")    time.sleep(0.5)

圆周率计算

#!/usr/bin/env python3# -*- coding: UTF-8 -*-import randompi = 0N = 100for k in range(N):    pi += 1 / pow(16,k) * \          (4 / (8 * k + 1) - \           2 / (8 * k + 4) - \           1 / (8 * k + 5) - \           1 /(8 * k + 6))print("pi = {}".format(pi))====================== RESTART: C:\Python3.7.0\test.py ======================pi = 3.141592653589793

蒙特卡罗方法#!/usr/bin/env python3# -*- coding: UTF-8 -*-from random import randomfrom time import perf_counterDARTS = 1000 * 1000hits = 0.0start = perf_counter()for i in range(1,DARTS + 1):    x,y = random(),random()    dist = pow(x ** 2 + y ** 2,0.5)    if dist < 1.0:        hits = hits + 1pi = 4 * (hits / DARTS)print("pi = {}".format(pi))print("The time is :{:.5f}s".format(perf_counter() - start))====================== RESTART: C:\Python3.7.0\test.py ======================pi = 3.14154The time is :0.88162s>>> ====================== RESTART: C:\Python3.7.0\test.py ======================pi = 3.139968The time is :0.86474s

转载于:https://my.oschina.net/hellopasswd/blog/2250077

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