【python】入门学习（三），,for循环for i

【python】入门学习（三），,for循环for i

for循环

for i in range(): #注意冒号 range中默认从0开始 或者从指定的数字开始 到给定数字的前一个数字结束 递增递减皆是如此

for循环提供变量的自动初始化

for i in range(10):    print(i,end = ‘ ‘)print()for i in range(5,10):    print(i,end = ‘ ‘)print()for i in range(10,0,-1):    print(i, end = ‘ ‘)print()

>>> ================================ RESTART ================================>>> 0 1 2 3 4 5 6 7 8 9 5 6 7 8 9 10 9 8 7 6 5 4 3 2 1 

while循环：

需要自己初始化，可以包含一个else语句块

i = 0while i < 10:    print(i,end = ‘ ‘)    i = i + 1print()

当事先循环次数不确定时，无法用for循环 如：

#donesum.pytotal = 0s = input(‘input a number or "done":‘)while s != ‘done‘:    total = total + int(s)    s = input(‘input a number or "done":‘)print(‘the total is ‘ + str(total))

break #跳出循环

continue #进入下一次循环 少用较好

多层循环：

#timestable.pyfor row in range(1,10):    for col in range(1,10):        prod = row * col        if prod < 10:            print(‘ ‘, end = ‘‘)        print(row * col, " ", end = ‘‘)    print()

>>> ================================ RESTART ================================>>>  1   2   3   4   5   6   7   8   9   2   4   6   8  10  12  14  16  18   3   6   9  12  15  18  21  24  27   4   8  12  16  20  24  28  32  36   5  10  15  20  25  30  35  40  45   6  12  18  24  30  36  42  48  54   7  14  21  28  35  42  49  56  63   8  16  24  32  40  48  56  64  72   9  18  27  36  45  54  63  72  81 

【python】入门学习（三）