CODEWITHSUNDEEP
python
James
James

Reputation: 31738

How to continue in nested loops in Python

How can you continue the parent loop of say two nested loops in Python?

for a in b:
    for c in d:
        for e in f:
            if somecondition:
                <continue the for a in b loop?>

I know you can avoid this in the majority of cases but can it be done in Python?

Upvotes: 87

Views: 128954

Answers (8)

Ben
Ben

Reputation: 1291

#infinite wait till all items obtained
while True:
    time.sleep(0.5)
    for item in entries:
        if self.results.get(item,None) is None:
            print(f"waiting for {item} to be obtained")
            break #continue outer loop
    else:
        break
    #continue

I wish there could be a labeled loop ...

Upvotes: 0

Ignacio Javier Kairuz Eguia
Ignacio Javier Kairuz Eguia

Reputation: 11

lista = ["hello1", "hello2" , "world"]

for index,word in enumerate(lista):
    found = False
    for i in range(1,3):
        if word == "hello"+str(i):
            found = True
            break
        print(index)
    if found == True:
        continue
    if word == "world":
        continue
    print(index)

Now what's printed :

>> 1
>> 2
>> 2

This means that the word no.1 ( index = 0 ) appeard first (there's no way for something to be printed before the continue statement). The word no.2 ( index = 1 ) appeared second ( the word "hello1" managed to be printed but not the rest ) and the word no.3 appeard third what mean's that the words "hello1" and "hello2" managed to be printed before the for loop reached this said third word.

To sum up it's just using the found = False / True boolean and the break statement.

Hope it helps!

Upvotes: 0

ChesIngosan
ChesIngosan

Reputation: 21

Looking at All the answers here its all different from how i do it\n Mission:continue to while loop if the if condition is true in nested loop

chars = 'loop|ing'
x,i=10,0
while x>i:
    jump = False
    for a in chars:
      if(a = '|'): jump = True
    if(jump==True): continue

Upvotes: 1

Samourai
Samourai

Reputation: 31

use a boolean flag

problem = False
for a in b:
  for c in d:
    if problem:
      continue
    for e in f:
        if somecondition:
            problem = True

Upvotes: 3

Tony The Lion
Tony The Lion

Reputation: 63200

You use break to break out of the inner loop and continue with the parent

for a in b:
    for c in d:
        if somecondition:
            break # go back to parent loop

Upvotes: 20

John La Rooy
John La Rooy

Reputation: 304175

from itertools import product
for a in b:
    for c, e in product(d, f):
        if somecondition:
            break

Upvotes: 13

Eric
Eric

Reputation: 97591

Here's a bunch of hacky ways to do it:

  1. Create a local function

    for a in b:
    def doWork():
        for c in d:
            for e in f:
                if somecondition:
                    return # <continue the for a in b loop?>
    doWork()

    A better option would be to move doWork somewhere else and pass its state as arguments.

  2. Use an exception

    class StopLookingForThings(Exception): pass

for a in b:
    try:
        for c in d:
            for e in f:
                if somecondition:
                    raise StopLookingForThings()
    except StopLookingForThings:
        pass

Upvotes: 30

Duncan
Duncan

Reputation: 95652

  1. Break from the inner loop (if there's nothing else after it)
  2. Put the outer loop's body in a function and return from the function
  3. Raise an exception and catch it at the outer level
  4. Set a flag, break from the inner loop and test it at an outer level.
  5. Refactor the code so you no longer have to do this.

I would go with 5 every time.

Upvotes: 84

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