给定以下代码(不起作用):
while True:
# Snip: print out current state
while True:
ok = get_input("Is this ok? (y/n)")
if ok.lower() == "y": break 2 # This doesn't work :(
if ok.lower() == "n": break
# Do more processing with menus and stuff
有办法解决这个问题吗?还是我必须先检查一次,跳出输入循环,然后再检查一次,如果用户满意,再跳出外部循环?
Break for外层和内部while循环:
while True:
while True:
print('Breaks inner "while" loop')
break # Here
print('Breaks outer "while" loop')
break # Here
或者,用if语句中断外部和内部while循环:
while True:
while True:
if True:
print('Breaks inner "while" loop')
break # Here
print('Breaks outer "while" loop')
break # Here
输出:
Breaks inner "while" loop
Breaks outer "while" loop
Break for outer和inner for循环:
for _ in iter(int, 1):
for _ in iter(int, 1):
print('Breaks inner "for" loop')
break # Here
print('Breaks outer "for" loop')
break # Here
或者,用if语句打破外部和内部for循环:
for _ in iter(int, 1):
for _ in iter(int, 1):
if True:
print('Breaks inner "for" loop')
break # Here
print('Breaks outer "for" loop')
break # Here
输出:
Breaks inner "for" loop
Breaks outer "for" loop
使用numpy.ndindex可以简单地将多个循环转换为单个、可破坏的循环
for i in range(n):
for j in range(n):
val = x[i, j]
break # still inside the outer loop!
for i, j in np.ndindex(n, n):
val = x[i, j]
break # you left the only loop there was!
您确实需要索引到对象中,而不是显式地遍历值,但至少在简单的情况下,它似乎比大多数答案所建议的要简单大约2-20倍。
Break for外层和内部while循环:
while True:
while True:
print('Breaks inner "while" loop')
break # Here
print('Breaks outer "while" loop')
break # Here
或者,用if语句中断外部和内部while循环:
while True:
while True:
if True:
print('Breaks inner "while" loop')
break # Here
print('Breaks outer "while" loop')
break # Here
输出:
Breaks inner "while" loop
Breaks outer "while" loop
Break for outer和inner for循环:
for _ in iter(int, 1):
for _ in iter(int, 1):
print('Breaks inner "for" loop')
break # Here
print('Breaks outer "for" loop')
break # Here
或者,用if语句打破外部和内部for循环:
for _ in iter(int, 1):
for _ in iter(int, 1):
if True:
print('Breaks inner "for" loop')
break # Here
print('Breaks outer "for" loop')
break # Here
输出:
Breaks inner "for" loop
Breaks outer "for" loop
你可以使用一个标志来打破循环:
if found:
break
这里,'found'是标志,你最初将它设置为False,然后在循环中使用这段代码。
found = False
for table_height in range(500):
if found:
break
下面是三个for循环的完整代码:
found = False
for table_height in range(500):
if found:
break
for cat_height in range(500):
if found:
break
for tort_height in range(500):
equation1 = table_height + cat_height == tort_height + 170
equation2 = table_height + tort_height == cat_height + 130
if equation1 and equation2:
print('table', table_height, ' cat', cat_height, ' tortoise', tort_height)
found = True
break
在这段代码中,如果等式1和等式2为True,它将设置'found'标志为True,并跳出最里面的for循环,它也将跳出其他两个for循环,因为'found'为True。