分支结构:
1.单分支结构:
# 猜数字 while True : a = eval(input()) if(a == 55): print("猜对了!") break
2.二分支结构:
# 猜数字 while True : a = eval(input()) if(a == 55): print("猜对了!") break else: print("下次一定对!!")
紧凑形式:用于简单表达式的二分支结构
# <表达式1> if <条件> else <表达式2> guess = eval(input()) print("猜{}了".format("对" if guess == 55 else "错"))
3.多分支结构:
# 猜数字 while True : a = eval(input()) if(a > 55): print("太大了!") elif(a < 55): print("太小了!") else: print("猜对了!") break
4.条件判断:
# 猜数字 while True : a = eval(input()) if(a > 55 and a < 57): print("猜对了!") break
5.异常处理:
try : num = eval(input()) print(num**2) except: print("输入非数字!") try : num = eval(input()) print(num**2) except NameError : # 标注异常类型之后,仅响应该异常异常类型名字等同于变量 print("输入非数字!")
6.身体质量指数BMI:
height,weight = eval(input("请输入身高(米)和体重(千克)[逗号隔开]:")) bmi = weight / pow(height,2) print("BMI数值为:{:.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国际指标'{}',国内指标'{}'".format(who,nat))
循环结构:
1.遍历循环:
for i in range(6) : print(i) ''' 0 1 2 3 4 5 ''' for i in range(1,6) : print(i) ''' 1 2 3 4 5 ''' for i in range(1,6,2) : print("Hello:",i) # 注意输出的空格 ''' Hello: 1 Hello: 3 Hello: 5 ''' for c in "Python123" : # 遍历字符串 print(c,end = "-") # P-y-t-h-o-n-1-2-3- for item in [123,"Py",456] : # 遍历列表 print(item,end = ',') # 123,Py,456, # 文件遍历循环
2.无限循环(条件循环):
while True : print("hahah")
3.循环控制保留字(continue、break):不想写。。。太懒了
4.循环的扩展:
for c in "PyThon" : if c == 'T' : break print(c,end = '') else : print("正常退出") # Py
while同上
2021-01-25