I. Jumping out of a single cycle
Regardless of the programming language, there may be a need to jump out of a loop, such as when enumerating, and terminating when you find a number that satisfies a condition. Jumping out of a single loop is simple, for example:
for i in range(10):
if i > 5:
print i
break
However, we sometimes need to jump out of multiple loops, and break is only able to jump out of one layer of the loop, for example:
for i in range(10):
for j in range(10):
if i+j > 5:
print i,j
break
Such code does not mean that it stops when it finds a set i+j > 5, but that it finds 10 sets in a row, because break only jumps out of the for j in range(10) loop. So, how can I jump out of the multiple? Here is a memo.
II. Jumping out of multiple loops
In fact, Python's standard syntax doesn't support jumping out of multiple loops, so you have to utilize a few tricks, roughly along the lines of writing as a function, utilizing Cartesian products, and utilizing debugging.
Of course the most common way of thinking about this is to use the variable labeling method
def f():
flag = 0
for i in range(10):
for j in range(i):
if i+j>5:
print i,j
flag = 1
break
if flag == 1:
break
if __name__ == "__main__":
f()
Write as a function
In Python, a function runs to the phrase return and stops, so you can take advantage of this feature by writing the function as a function that terminates multiple loops.
Example:
def work():
for i in range(10):
for j in range(10):
if i+j > 5:
return i,j
print work()
Using the Cartesian product
The idea of this approach is that since I can jump out of a single loop, I rewrite the multiple loops as a single loop, which can be done using the Cartesian product function product in itertools, for example:
from itertools import product
for i,j in product(range(10), range(10)):
if i+j > 5:
print i,j
break
Utilizing debug mode
The Cartesian product approach is clever and concise, but it can only be used in situations where the set of each loop is independent; if each layer of the loop is closely related to the previous layer, you can't use this technique. This time you can use the first method, it will be written as a function, in addition, you can also use debug mode. This one utilizes the principle of debugging mode, which exits whenever an error is reported, and it fakes an error out.
class Found(Exception):
pass
try:
for i in range(10):
for j in range(i): # The second loop is related to the first
if i + j > 5:
raise Found
except Found:
print i, j
Above is the inventory Python interrupt multiple loop ideas in detail, more please pay attention to my other related articles!