Python append to begin

How to Append String to Beginning Of List Python

This Python tutorial will show us various approaches to adding a string to the beginning of a list in Python. Because the list insertion technique must be the same irrespective of what type of data the list includes, a list of strings is going to be used examples throughout the course to concentrate on list insertion rather than inserting other data types.

Append String To Beginning of List Python

The new element is often added at the end of a Python list using the append function. However, there are some circumstances where we must append each entry we add to the beginning of the list. Let’s talk about some methods for doing an append at the start of the list.

To append a string to the beginning of a list in Python, use the insert() function

The insert() function adds a new item to an existing list at the specified index. It accepts two parameters: the value to insert and the index into which the item should be entered.

As an illustration, we’ll add a string to a three-item existing list. By setting the first argument to 0, which indicates that the insertion is made at index 0 (the list’s start), we use insert() function to append a string at the beginning of the list.

Create or initialize the new list with three strings that represent the three cities of the USA using the below code.

usa_citi = ["New York","Los Angeles", "Chicago"] print(usa_citi)

Use the function insert() to insert the new string “Dallas” at the beginning of the above-created list.

Print the values of the list “usa_citi” using the below code.

In the above output, we can see that the string “Dallas” is appended at the beginning of the list.

To append a string to the beginning of a list in Python, use the + and [] Operator

The string appending at the beginning task can be completed by combining these two operators in Python. The element is transformed into a list, and the list addition is then carried out.

Create or initialize the new list with three strings that represent the three cities of the USA using the below code.

usa_citi = ["New York","Los Angeles", "Chicago"] print(usa_citi)

Use the operators + and [] to append the string “Dallas” to the beginning of the above-created list “usa_citi” using the below code.

usa_citi = ["Dallas"] + usa_citi

Keep in mind that the string “Dallas” is enclosed in square brackets []. In order to enable list addition, the single string is transformed into the list data type.

View the list using the below code.

In the above output, we can see that the string “Dallas” is appended at the beginning of the list using the two operators + and [].

This is how to append a string to the beginning of a list in Python, using the + and [] Operator.

To append a string to the beginning of a list in Python, use the slicing method

List slicing is yet another way to carry out this specific operation. We simply attach the list created from the transformed element to the 0-sliced list in Python.

Create or initialize the new list with three strings that represent the three cities of the USA using the below code.

usa_citi = ["New York","Los Angeles", "Chicago"] print(usa_citi)

Use the slicing to append the string at the beginning of the above-created list using the below code.

Check the appended string at the beginning of the list using the below code.

This is how to append a string to the beginning of a list in Python, using the slicing method.

Append an element at the start of a Python list using unpacking

In Python, a procedure called unpacking makes certain iterable manipulations possible. The iterable assignment is more adaptable and effective for developers because of unpacking.

In this example, inserting at the start of the list will be accomplished by merging already-existing iterables, which is a feature of unpacking. We combine a single string with the current list using the unpacking operator *, inserting the string at the start of the newly created list.

Create or initialize the new list with three strings that represent the three cities of the USA using the below code.

usa_citi = ["New York","Los Angeles", "Chicago"] print(usa_citi)

Use the unpacking method to append the string at the beginning of the above-created list using the below code.

new_str = "Seattle" usa_citi = [new_str,*usa_citi]

Show the newly appended string to the list using the below code.

This is how to append an element at the start of a list using unpacking in Python.

To append a string to the beginning of a list in Python, use the collections.deque.appendleft() method

The list can be transformed into a deque, and then the push-like action can be carried out at the beginning of the doubly-ended queue using appendleft().

Import the required libraries or methods using the below code.

from collections import deque

Create or initialize the new list with three strings that represent the three cities of the USA using the below code.

usa_citi = ["New York","Los Angeles", "Chicago"] print(usa_citi)

First deque the above-created list using the below code.

Append the new string “Dallas” at the beginning of the list using the below code.

Again convert it into the list using the below code.

View the list using the below code.

This is how to append a string to the beginning of a list in Python, using the collections.deque.appendleft() method.

We have learned about how to append the string at the beginning of the List in Python using different approaches or methods such as using the insert(), plus(+), and square brackets([]) operator, slicing, unpacking, and deque() method.

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8 ways to add an element to the beginning of a list and string in Python

Let’s look at different methods for adding elements to the beginning of a list and string: concatenation, insert, append, extend, rjust, and f-strings.

How to add an item to the top of a Python list: 4 methods

Lists in Python are mutable and ordered data structures designed to store a group of values. If you need to insert an element in the first position of an existing list during the program execution, you can use one of the methods described below.

Method 1: insert

This method is implemented using the built-in insert() method of lists. This method works with any type of data and allows you to insert the desired element at any position in the existing list, including the first one. The insert() method takes two parameters – the index (position) at which the element is to be inserted, and the element itself. Counting positions in Python starts from zero – Accordingly, to insert an element at the beginning of the list , you need to specify 0 , and not, as the first parameter 1 . Let’s take an example. Suppose we have a list [1, 2, 3] where we want to insert the number 5 at the beginning. Use the insert() method:

arr = [1, 2, 3] arr.insert(0, 5) print(arr) 

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Python append to begin

С помощью конкатенации (сложения) тоже можно вставить нужный элемент в начало списка. Правда, для этого нужно, чтобы элемент был представлен в виде списка:

Результат будет таким же, как и в первом способе:

Способ 3: метод append

Этот метод по умолчанию расширяет существующий список, добавляя элемент в конец. Но ничто не мешает расширить список, состоящий из единственного элемента:

sp = [1, 2, 3] num = [5] num.append(sp) print(num) 

Результат при использовании append() отличается – получится вложенный список:

Нужный элемент, однако, получает индекс 0 , так что цель достигнута. Кроме того, при решении некоторых задач может потребоваться создание именно вложенного списка, поэтому способ имеет право на жизнь.

Способ 4: метод extend

Метод extend() похож на append() – с той разницей, что он сохраняет «одномерность» списка:

sp = [1, 2, 3] num = [5] num.extend(sp) print(num) 

Результат – обычный, не вложенный, список:

Отметим, что одномерность сохранится даже в том случае, если элемент, который нужно поставить в начало списка, сам является списком, состоящим из нескольких элементов:

sp = [1, 2, 3] num = [5, 6, 7] num.extend(sp) print(num) 

4 способа добавления элемента в начало строки в Python

Строки в Python относятся к неизменяемому типу данных str , и представляют собой последовательности различных символов. Поскольку строки не изменяются, добавить элементы в начало последовательности можно только путем создания новой строки.

Способ 1: конкатенация

Строки в Python можно соединять (результатом будет новая строка). Рассмотрим на примере вставки знака + в начало строки, содержащей абстрактный мобильный номер:

el = '+' num = '91956612345' print(el + num) 

Результатом операции станет новая строка:

Способ 2: использование f-строки

Вставить элемент в начало строки можно также с помощью f-строки:

el = '+' num = '91956612345' print(f'') 

Результат будет аналогичным первому способу:

Способ 3: преобразование в список

Если нужно вставить элемент в определенную позицию строки, в том числе – в начало, можно последовательно воспользоваться преобразованием строки в список и объединением списка в строку с помощью метода join():

el = '+' num = list('91956612345') (num).insert(0, el) print(''.join(num)) 

Способ 4: использование rjust

Метод rjust() используется для выравнивания строки по правому краю. В качестве параметров он принимает длину новой строки и символ, которым будут заполнены пустые позиции. По умолчанию в качестве заполнителя используется пробел, но ничто не мешает выбрать знак + :

num = "91956612345" print(num.rjust(12, '+')) 

В результате получится нужная строка, в начало которой вставлен необходимый символ:

Подведем итоги

Мы рассмотрели восемь простых и практичных способов добавления нужного элемента в начало списка и строки Python. Знаете какие-нибудь другие интересные способы вставки элементов? Поделитесь с нами в комментариях.

Материалы по теме

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Append to Front of a List in Python

1. Use insert() to Append an Element to the Front of a List in Python
2. Use the + Operator to Append an Element to the Front of a List in Python
3. Use Unpacking to Insert an Element Into the Beginning of a List

This tutorial will demonstrate different ways on how to append an element to the front of a list in Python.

Throughout the tutorial, a list of integers will be used as examples to focus on list insertion instead of inserting various data types since the list insertion approach should be the same regardless of what data type the list contains.

Use insert() to Append an Element to the Front of a List in Python

The insert() function inserts an element to the given index of an existing list. It accepts two parameters, the index to be inserted into and the value to insert.

For example, we’ll insert an element into an existing list of size 5 . To append an element to the front of the list using this function, we should set the first argument as 0 , which denotes that the insertion is done at index 0 — the beginning of the list.

int_list = [13, 56, 5, 78, 100]  int_list.insert(0, 24)  print(int_list) 

Use the + Operator to Append an Element to the Front of a List in Python

Another approach to append an element to the front of a list is to use the + operator. Using the + operator on two or more lists combines them in the specified order.

If you add list1 + list2 together, then it concatenates all the elements from list2 after the last element of list1 . For example, let’s add a single integer into the beginning of an already existing list using the + operator.

to_insert = 56 int_list = [13, 5, 78, 19, 66]  int_list = [to_insert] + int_list  print(int_list) 

Notice the to_insert variable is encapsulated with square brackets [] . This is done to convert the single integer into the list data type to make list addition possible.

Use Unpacking to Insert an Element Into the Beginning of a List

Unpacking is an operation in Python that allows unique iterable manipulations to be possible. Unpacking allows iterable assignment to be more flexible and efficient for the developers.

Unpacking also allows merging existing iterables, which is the operation that will be used to insert into the beginning of the list for this example.

To append an element to the beginning of a list using unpacking, we use the unpacking operator * to merge the single integer and the existing list, placing the integer at the beginning of the newly formed list.

to_insert = 7 int_list = [19, 22, 40, 1, 78]  int_list = [to_insert, *int_list]  print(int_list) 

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