How to Stop a for Loop

how to stop a for loop

Use break and continue to do this. Breaking nested loops can be done in Python using the following:

for a in range(...):
   for b in range(..):
      if some condition:
         # break the inner loop
         break
   else:
      # will be called if the previous loop did not end with a `break` 
      continue
   # but here we end up right after breaking the inner loop, so we can
   # simply break the outer loop as well
   break

Another way is to wrap everything in a function and use return to escape from the loop.

How to stop a JavaScript for loop?

To stop a for loop early in JavaScript, you use break:

var remSize = [], 
    szString,
    remData,
    remIndex,
    i;

/* ...I assume there's code here putting entries in `remSize` and assigning something to `remData`... */

remIndex = -1; // Set a default if we don't find it
for (i = 0; i < remSize.length; i++) {      
     // I'm looking for the index i, when the condition is true
     if (remSize[i].size === remData.size) {
          remIndex = i;
          break;       // <=== breaks out of the loop early
     }
}

If you're in an ES2015 (aka ES6) environment, for this specific use case, you can use Array's findIndex (to find the entry's index) or find (to find the entry itself), both of which can be shimmed/polyfilled:

var remSize = [], 
    szString,
    remData,
    remIndex;

/* ...I assume there's code here putting entries in `remSize` and assigning something to `remData`... */

remIndex = remSize.findIndex(function(entry) {
     return entry.size === remData.size;
});

find stops the first time the callback returns a truthy value, returning the element that the callback returned the truthy value for (returns undefined if the callback never returns a truthy value):

var remSize = [], 
    szString,
    remData,
    remEntry;

/* ...I assume there's code here putting entries in `remSize` and assigning something to `remData`... */

remEntry = remSize.find(function(entry) {
     return entry.size === remData.size;
});

findIndex stops the first time the callback returns a truthy value, returning the index of the element instead of the element; it returns -1 if the callback never returns a truthy value.

If you're using an ES5-compatible environment (or an ES5 shim), you can use the new some function on arrays, which calls a callback until the callback returns a truthy value:

var remSize = [], 
    szString,
    remData,
    remIndex;

/* ...I assume there's code here putting entries in `remSize` and assigning something to `remData`... */

remIndex = -1; // <== Set a default if we don't find it
remSize.some(function(entry, index) {
    if (entry.size === remData.size) {
        remIndex = index;
        return true; // <== Equivalent of break for `Array#some`
    }
});

If you're using jQuery, you can use jQuery.each to loop through an array; that would look like this:

var remSize = [], 
    szString,
    remData,
    remIndex;

/* ...I assume there's code here putting entries in `remSize` and assigning something to `remData`... */

remIndex = -1; // <== Set a default if we don't find it
jQuery.each(remSize, function(index, entry) {
    if (entry.size === remData.size) {
        remIndex = index;
        return false; // <== Equivalent of break for jQuery.each
    }
});

Break for loop in an if statement

You'll need to break out of each loop separately, as people have mentioned in the comments for your question, break only stops the loop which it's in

for x in userpassword[k]:
    for z in lowercaselist:
        if x in z:
            newpasswordlist.append(z)
            k +=1
            break
    if x in z: # added an extra condition to exit the main loop
        break

You'll need to do this for both loops. If you want to break out of the while loop as well, then you can add if x in z: break in that loop as well.

Stop a For Loop at an Index Value

As you know the exact index to stop in the string you can provide the index to loop from and to

for i in train_times[:20]:
    print('There is a train at {}'.format(i))
    print('--------------------------------------')

End loop with counter and condition

The for loop is slightly more performant than the while because range() is implemented in C, meanwhile the += operation is interpreted and requires more operations and object creation/ destruction. You can illustrate the performance difference using the timeit module, for example:

from timeit import timeit

def for_func():
    for i in range(10000):
        result = int(i)
        if result == -1: 
            break

def while_func():
    i = 0
    result = 1
    while result != -1 and i < 10000:
        result = int(i)
        i += 1

print(timeit(lambda: for_func(), number = 1000))
# 1.03937101364
print(timeit(lambda: while_func(), number = 1000))
# 1.21670079231 

The for loop is arguably more Pythonic in the vast majority of cases when you wish to iterate over an iterable object. Furthermore, to quote the Python wiki: "As the for loop in Python is so powerful, while is rarely used except in cases where a user's input is required". There is nothing un-Pythonic about using a break statement per se.

Readability is mostly subjective, I would say the for loop is more readable too, but it probably depends on your previous programming background and experience.

How to Stop a For Loop when a value is found from a .csv file

you mean like this:

import csv

fileName = 'sip.csv'
READ = 'r'
WRITE = 'w'
check = True

enter_code = input('Enter The Sip Response Code: ')
with open(fileName, READ) as myXLfile:
    dataFromFile = csv.reader(myXLfile, delimiter=";")
    for currentRow in dataFromFile:
        if enter_code == currentRow[0]:
            print("The SIP Response Code you entered is: " + enter_code)
            print("The SIP Message is:  " + currentRow[1])
            print("Meaning:  " + currentRow[2])
            check = False
            break
    if check:
        print("Im Sorry, I Do not have this Response Code")
    else:
        print("Thank You and Goodbye")

How to stop IT loop in FOR loop without stopping the FOR loop

You can use the continue keyword.
It allows you to ignore everything that comes next and go to the start of the loop.
For example in this case:

for i in (0, 1, 2):
   print(i)
   continue
   print("This won't get executed")

The line after the continue will never run.

How to stop a while loop after n iterations?

The short answer is that you need to add a n += 1 in the while loops, like that:

def easy_level():
  n= 0
  while n < 10:
    user_number=int(input('Guess the number: '))
    if user_number > number:
      print('Too high')
    elif user_number < number:
      print('Too low')
    elif user_number == number:
      print(f'You guessed the number {number}! Congratulations!')
      play_again=input('Would you like to play again? type y for yes or n for no: ')
      if play_again =='y':
        levels()
      else:
        print('Bye')
         break

    n += 1

  print('Sorry, no more attempts :(')

Long answer is that you should really consider using a for loop instead, here is an example of how you can do that:

def easy_level():
  for i in range(10)
    user_number=int(input('Guess the number: '))
    if user_number > number:
      print('Too high')
    elif user_number < number:
      print('Too low')
    elif user_number == number:
      print(f'You guessed the number {number}! Congratulations!')
      play_again=input('Would you like to play again? type y for yes or n for no: ')
      if play_again =='y':
        levels()
      else:
        print('Bye')
         break

  print('Sorry, no more attempts :(')

And you should make your script a lot cleaner by removing the repetitive code like this:

from random import *

def chooseLevel():
  user_level=input('Type E for easy level and D for difficult level: ')
  if user_level=='e':
    return 10
  else:
    return 5

number = randint(1,100)
for i in range(chooseLevel()):
    user_number = int(input('Guess the number: '))
    if user_number > number:
      print('Too high')
    elif user_number < number:
      print('Too low')
    elif user_number == number:
      print(f'You guessed the number {number}! Congratulations!')
      play_again = input('Would you like to play again? type y for yes or n for no: ')
      if play_again =='y':
        levels()
      else:
        print('Bye')
         break

  print('Sorry, no more attempts :(')

Here I removed the two functions that you had and I made it so that there is only one loop which makes the code a lot cleaner, I also changed the levels() function name to chooseLevel() to make it clearer on what the function does and I also added spaces between the = which makes things look cleaner.

I also used the for loop like this for i in range(chooseLevel())
Which means that if the chooseLevel() function returned a 5 it will be as if I wrote for i in range(5) and if the chooseLevel() function returns a 10 it will be as if I wrote for i in range(10)

Thanks.

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