python -day3

1、循环（new）

　　break   在子句中达成某条件时跳出循环

　　continue 在子句中达成某条件时重新执行循环

　   例：逢7跳过 

i = 0
while True:
    i += 1
# 排除7的倍数；十位为7；个位为7 三种情况
    if i%7 == 0 or i//10==7 or i%10==7:
        print('')
#结束判断，重新循环
        continue
    elif i>100:
#终止循环
        break
    else:
        print(i)

 

 

 

task 1 简易计算器：要求可以多次运算，且当输入运算符为‘q’ 时退出计算器

#申明第几次运算，因第一次和第n次（n≠1）运算方式不同
num_of_time = 1
#限定运算符号范围，在输入未知符号时报错并重新运算
o = ['+', '-', '*', '/', '**', '//', '%']
while True:
#第一次运算时
    if num_of_time == 1:
        result = float(input("第一个数字为："))
        operate = input("输入运算符:")
#实现当输入运算符为q时退出程序
        if operate =='q':
            print("end")
            break
        elif operate in o:
#实现简单运算
            second_num = float(input("第二个数字为:"))
            if operate == '+':
                result+=second_num
            elif operate == '-':
                result -= second_num
            elif operate == '*':
                result *= second_num
            elif operate == '/':
                result /= second_num
            elif operate == '**':
                result **= second_num
            elif operate == '//':
                result //= second_num
            elif operate == '%':
                result %= second_num
        else:
            print('wrong operate!')
            continue
        print(float(result))
        num_of_time+=1
        print("当前第%d次运算"% num_of_time)
#当非第一次运算时
    else:
        operate = input("输入运算符:")
        if operate == 'q':
            print("end")
            break
        elif operate in o:
            second_num = float(input("第二个数字为:"))
            if operate == '+':
                result += second_num
            elif operate == '-':
                result -= second_num
            elif operate == '*':
                result *= second_num
            elif operate == '/':
                result /= second_num
            elif operate == '**':
                result **= second_num
            elif operate == '//':
                result //= second_num
            elif operate == '%':
                result %= second_num
        else:
            print('wrong operate!')
            continue
        print(float(result))
        num_of_time += 1
        print("当前第%d次运算" % num_of_time)

　　

 

 

函数版：

 

 

def calculator():
#全局变量
    global a
    global flag
    operate = input("运算符为：")
    if operate=='q':
        flag=1
#中断函数quit(),exit()等
        exit()
    b = float(input("第二个数字："))
    sign = ['+', '-', '*', '/', '**', '//', '%']
    if operate ==sign[0]:
        a+=b
    if operate ==sign[1]:
        a-=b
    if operate ==sign[2]:
        a *= b
    if operate ==sign[3]:
        a /= b
    if operate ==sign[4]:
        a **= b
    if operate ==sign[5]:
        a //= b
    if operate ==sign[6]:
        a %= b
    print("结果为"+str(a))



times=1
flag=0
a=float(input("第一个数字："))
while True:
    print("第%d次运算"% times)
    calculator()
    times+=1
    if flag==1:
        break