Breaking for loop python

How To Use Break, Continue, and Pass Statements when Working with Loops in Python 3

Using for loops and while loops in Python allow you to automate and repeat tasks in an efficient manner.

But sometimes, an external factor may influence the way your program runs. When this occurs, you may want your program to exit a loop completely, skip part of a loop before continuing, or ignore that external factor. You can do these actions with break , continue , and pass statements.

Prerequisites

You should have Python 3 installed and a programming environment set up on your computer or server. If you don’t have a programming environment set up, you can refer to the installation and setup guides for a local programming environment or for a programming environment on your server appropriate for your operating system (Ubuntu, CentOS, Debian, etc.)

Break Statement

In Python, the break statement provides you with the opportunity to exit out of a loop when an external condition is triggered. You’ll put the break statement within the block of code under your loop statement, usually after a conditional if statement.

Info: To follow along with the example code in this tutorial, open a Python interactive shell on your local system by running the python3 command. Then you can copy, paste, or edit the examples by adding them after the >>> prompt.

Let’s look at an example that uses the break statement in a for loop:

number = 0 for number in range(10): if number == 5: break # break here print('Number is ' + str(number)) print('Out of loop') 

In this small program, the variable number is initialized at 0. Then a for statement constructs the loop as long as the variable number is less than 10.

Within the for loop, there is an if statement that presents the condition that if the variable number is equivalent to the integer 5, then the loop will break.

Within the loop is also a print() statement that will execute with each iteration of the for loop until the loop breaks, since it is after the break statement.

To know when we are out of the loop, we have included a final print() statement outside of the for loop.

When we run this code, our output will be the following:

Output
Number is 0 Number is 1 Number is 2 Number is 3 Number is 4 Out of loop 

This shows that once the integer number is evaluated as equivalent to 5, the loop breaks, as the program is told to do so with the break statement.

The break statement causes a program to break out of a loop.

Continue Statement

The continue statement gives you the option to skip over the part of a loop where an external condition is triggered, but to go on to complete the rest of the loop. That is, the current iteration of the loop will be disrupted, but the program will return to the top of the loop.

The continue statement will be within the block of code under the loop statement, usually after a conditional if statement.

Using the same for loop program as in the Break Statement section above, we’ll use a continue statement rather than a break statement:

number = 0 for number in range(10): if number == 5: continue # continue here print('Number is ' + str(number)) print('Out of loop') 

The difference in using the continue statement rather than a break statement is that our code will continue despite the disruption when the variable number is evaluated as equivalent to 5. Let’s review our output:

Output
Number is 0 Number is 1 Number is 2 Number is 3 Number is 4 Number is 6 Number is 7 Number is 8 Number is 9 Out of loop 

Here, Number is 5 never occurs in the output, but the loop continues after that point to print lines for the numbers 6–10 before leaving the loop.

You can use the continue statement to avoid deeply nested conditional code, or to optimize a loop by eliminating frequently occurring cases that you would like to reject.

The continue statement causes a program to skip certain factors that come up within a loop, but then continue through the rest of the loop.

Pass Statement

When an external condition is triggered, the pass statement allows you to handle the condition without the loop being impacted in any way; all of the code will continue to be read unless a break or other statement occurs.

As with the other statements, the pass statement will be within the block of code under the loop statement, typically after a conditional if statement.

Using the same code block as above, let’s replace the break or continue statement with a pass statement:

number = 0 for number in range(10): if number == 5: pass # pass here print('Number is ' + str(number)) print('Out of loop') 

The pass statement occurring after the if conditional statement is telling the program to continue to run the loop and ignore the fact that the variable number evaluates as equivalent to 5 during one of its iterations.

We’ll run the program and consider the output:

Output
Number is 0 Number is 1 Number is 2 Number is 3 Number is 4 Number is 5 Number is 6 Number is 7 Number is 8 Number is 9 Out of loop 

By using the pass statement in this program, we notice that the program runs exactly as it would if there were no conditional statement in the program. The pass statement tells the program to disregard that condition and continue to run the program as usual.

The pass statement can create minimal classes, or act as a placeholder when working on new code and thinking on an algorithmic level before hammering out details.

Conclusion

The break , continue , and pass statements in Python will allow you to use for loops and while loops more effectively in your code.

To work more with break and pass statements, you can follow our project tutorial “How To Create a Twitterbot with Python 3 and the Tweepy Library.”

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Tutorial Series: How To Code in Python

Introduction

Python is a flexible and versatile programming language that can be leveraged for many use cases, with strengths in scripting, automation, data analysis, machine learning, and back-end development. It is a great tool for both new learners and experienced developers alike.

Prerequisites

You should have Python 3 installed and a programming environment set up on your computer or server. If you don’t have a programming environment set up, you can refer to the installation and setup guides for a local programming environment or for a programming environment on your server appropriate for your operating system (Ubuntu, CentOS, Debian, etc.)

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Циклы в Python: как работают и какие бывают

Они есть практически в каждом языке программирования, но в Python с ними работать приятнее всего. Как, впрочем, и со всем остальным.

Иллюстрация: Катя Павловская для Skillbox Media

Код в Python обычно выполняется последовательно: первая строка, потом вторая, третья и так далее. Но некоторые конструкции позволяют нарушать этот порядок, чтобы совершать более сложные операции.

Например, циклы выполняют один и тот же блок кода несколько раз. В Python есть два основных вида циклов: while и for. О них и поговорим.

Как работают циклы

Любой цикл состоит из двух обязательных элементов:

• условие — начальный параметр; цикл запустится только при его выполнении и закончится, как только условие перестанет выполняться;
• тело — сама программа, которая выполняется внутри цикла.

Схематически его можно представить так:

В синтаксисе Python в конце строки с условием ставится двоеточие, а всё тело выделяется отступом (табуляцией или четырьмя пробелами).

В Java и C++ такое достигается с помощью конструкции do while, но в Python её нет. Зато можно сделать аналог. Для этого нужно использовать бесконечный цикл, а внутри его тела прописать условие завершения.

Можно вкладывать друг в друга сколько угодно циклов. При этом для каждого нового уровня вложенности нужно увеличивать отступ. Выглядит это так:

while condition: pass while inner_condition: pass pass

Напишем программу, которая будет выводить номер итерации внешнего и внутреннего цикла.

for i in range(3): print(f'Итерация внешнего цикла: ') for j in range(2): print(f'Итерация внутреннего цикла: ') >>> Итерация внешнего цикла: 0 >>> Итерация внутреннего цикла: 0 >>> Итерация внутреннего цикла: 1 >>> Итерация внешнего цикла: 1 >>> Итерация внутреннего цикла: 0 >>> Итерация внутреннего цикла: 1 >>> Итерация внешнего цикла: 2 >>> Итерация внутреннего цикла: 0 >>> Итерация внутреннего цикла: 1

Резюмируем

• Циклы — один из основных инструментов любого Python-разработчика. С их помощью всего за пару строчек кода можно совершить сразу множество повторяющихся действий.
• Циклы состоят из условия и тела. Код в теле выполняется только до тех пор, пока соблюдено условие.
• В Python есть два вида циклов: while и for. В while условие задаётся явным образом. В for перебирается каждый элемент коллекции.
• К обоим видам можно применять разные операторы: break для прерывания, continue для пропуска части тела, else для совершения последнего действия перед выходом из цикла.
• Циклы можно делать бесконечными (тогда программа никогда не завершится или завершится только при выполнении определённого условия) и вкладывать друг в друга.

Больше интересного про код в нашем телеграм-канале. Подписывайтесь!

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То есть объект, который может возвращать элементы по одному.

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How To Control Python For Loop with Break Statement?

Python provides for loops in order to iterate over the given list, dictionary, array, or similar iterable types. During iteration, we may need to break and exit from the loop according to the current condition. In this tutorial, we will look at how to break a python for loop with break statement with different examples.

Break Syntax

break statement has very simple syntax where we only use the break keyword. We generally check for a condition with if-else blocks and then use break .

Break For Loop After Given Step

We can use break after a given step count. We will count the steps and then run break at the given count with if condition check. In this example, we have ranges from 1 to 10 but we will break after the 5th step.

for i in range(1,10): print(i) if(i>=5): break

Break For Loop After Specified Condition

Another useful case for breaking for loop is check given condition which can be different and calculated for each step. In this example, we will sum each step i value and check whether the sum is bigger than 20. If it goes beyond 20 we will terminate for a loop.

mysum=0 for i in range(1,10): mysum=mysum+i print(mysum) if(mysum>20): break

Break List For Loop

The list is a very popular data type used in Python programming languages and we will generally use list types in order to loop and break. In this example, we will loop in a list and break the list loop if the current element is equal to 5.

for i in [1,23,34,6,5,79,0]: print(i) if(i==5): break

Break Dictionary For Loop

Dictionary is another popular type used in Python programming language. We can check the given dictionary current element key and value in order to break for a loop. In this example, we will look current value and break the loop if it is end .

mydict= for k,v in mydict.items(): print(v) if(v=='end'): break

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