Python Language Loops Break and Continue in Loops
Example
break statement
When a break statement executes inside a loop, control flow "breaks" out of the loop immediately:
i = 0
while i < 7:
print(i)
if i == 4:
print("Breaking from loop")
break
i += 1
The loop conditional will not be evaluated after the break statement is executed. Note that break statements are only allowed inside loops, syntactically. A break statement inside a function cannot be used to terminate loops that called that function.
Executing the following prints every digit until number 4 when the break statement is met and the loop stops:
0
1
2
3
4
Breaking from loop
break statements can also be used inside for loops, the other looping construct provided by Python:
for i in (0, 1, 2, 3, 4):
print(i)
if i == 2:
break
Executing this loop now prints:
0
1
2
Note that 3 and 4 are not printed since the loop has ended.
If a loop has an else clause, it does not execute when the loop is terminated through a break statement.
continue statement
A continue statement will skip to the next iteration of the loop bypassing the rest of the current block but continuing the loop. As with break, continue can only appear inside loops:
for i in (0, 1, 2, 3, 4, 5):
if i == 2 or i == 4:
continue
print(i)
0
1
3
5
Note that 2 and 4 aren't printed, this is because continue goes to the next iteration instead of continuing on to print(i) when i == 2 or i == 4.
Nested Loops
break and continue only operate on a single level of loop. The following example will only break out of the inner for loop, not the outer while loop:
while True:
for i in range(1,5):
if i == 2:
break # Will only break out of the inner loop!
Python doesn't have the ability to break out of multiple levels of loop at once -- if this behavior is desired, refactoring one or more loops into a function and replacing break with return may be the way to go.
Use return from within a function as a break
The return statement exits from a function, without executing the code that comes after it.
If you have a loop inside a function, using return from inside that loop is equivalent to having a break as the rest of the code of the loop is not executed (note that any code after the loop is not executed either):
def break_loop():
for i in range(1, 5):
if (i == 2):
return(i)
print(i)
return(5)
If you have nested loops, the return statement will break all loops:
def break_all():
for j in range(1, 5):
for i in range(1,4):
if i*j == 6:
return(i)
print(i*j)
will output:
1 # 1*1
2 # 1*2
3 # 1*3
4 # 1*4
2 # 2*1
4 # 2*2
# return because 2*3 = 6, the remaining iterations of both loops are not executed
