Методы и элементы данных класса array() в Python.

Свойство array.typecode возвращает символ typecode , используемый для создания массива array .

array.itemsize :

Свойство array.itemsize возвращает длину в байтах одного элемента массива array во внутреннем представлении.

array.append(x) :

Метод array.append() добавляет новый элемент со значением x в конец массива array .

array.buffer_info() :

Метод array.buffer_info() возвращает кортеж (address, length) с текущим адресом памяти address и длиной length в элементах буфера, используемых для хранения содержимого массива. Размер буфера памяти в байтах может быть получен как array.buffer_info()[1] * array.itemsize . Это иногда полезно при работе с низкоуровневыми и небезопасными интерфейсами ввода-вывода, которым требуются адреса памяти, такие как определенные операции ioctl() . Возвращенные числа действительны до тех пор, пока существует массив и к нему не применяются операции с изменением длины.

Примечание. При использовании объектов массива из кода, написанного на C или C++, имеет смысл использовать интерфейс буфера, поддерживаемый объектами массива. Этот метод поддерживается для обратной совместимости и его следует избегать в новом коде. Интерфейс буфера задокументирован в Buffer Protocol.

array.byteswap() :

Метод array.byteswap() меняет порядок байтов каждого элемента в массиве . Метод поддерживает только значения размером 1, 2, 4 или 8 байт. Для других типов значений вызывается исключение RuntimeError .

Метод array.byteswap() полезно использовать при чтении данных из файла, записанного на машине с другим порядком байтов.

array.count(x) :

Метод array.count() вернет количество вхождений аргумента x в массиве array .

array.extend(iterable) :

Метод array.extend() добавляет элементы из итерируемого объекта iterable в конец массива array .

Если iterable — это другой массив array , он должен иметь точно такой же typecode . Если typecode другой, то появится исключение TypeError . Если iterable не является массивом array , то он должен быть повторяемым, а его элементы должны иметь правильный тип для добавления в массив.

array.frombytes(s) :

Метод array.frombytes() добавляет элементы из строки, интерпретируя строку как массив машинных значений. Как если бы она была прочитана из файла с помощью метода array.fromfile() .

array.fromfile(fp, n) :

Метод array.fromfile() считывает n элементов (как машинные значения) из файлового объекта fp и добавляет их в конец массива.

Если доступно менее n элементов, вызывается исключение EOFError , но при этом доступные элементы вставляются в массив. Аргумент fp должен быть настоящим файловым объектом. Для чтения массива из фала метод file.read() не подойдет.

array.fromlist(list) :

Метод array.fromlist() добавляет элементы массив array из списка list . Это эквивалентно добавлению x в список array.append(x) , за исключением того, что в случае ошибки типа массив array не изменяется.

array.fromunicode(s) :

Метод array.fromunicode() расширяет массив array данными из заданной строки s в Unicode. Массив array должен быть массивом типа 'u' , в противном случае поднимается исключение ValueError .

Используйте array.frombytes(unicodestring.encode(enc)) , чтобы добавить данные Unicode в массив другого типа.

array.index(x[, start[, stop]]) :

Метод array.index() возвращает наименьшее целое число i , где i является индексом первого вхождения значения x в массив array .

Необязательные аргументы start и stop (доступны с Python 3.10) могут быть указаны для поиска x в части массива. Поднимает ValueError , если x не найден.

Изменено в версии 3.10: Добавлены необязательные аргументы start и stop .

Как превратить string representation numpy.array в обычный List?

Я хочу его превратить в обычный список. Должно быть вот так:

Т. е. я хочу убрать скобки и преобразовать numpy.ndarray в list . Пробовал использовать ast.literal_eval , но не работает.

Как сделать это преобразование?

Всё ещё ищете ответ? Посмотрите другие вопросы с метками python строки list numpy или задайте свой вопрос.

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Python List/Array Methods

Python has a set of built-in methods that you can use on lists/arrays.

Method	Description
append()	Adds an element at the end of the list
clear()	Removes all the elements from the list
copy()	Returns a copy of the list
count()	Returns the number of elements with the specified value
extend()	Add the elements of a list (or any iterable), to the end of the current list
index()	Returns the index of the first element with the specified value
insert()	Adds an element at the specified position
pop()	Removes the element at the specified position
remove()	Removes the first item with the specified value
reverse()	Reverses the order of the list
sort()	Sorts the list

Note: Python does not have built-in support for Arrays, but Python Lists can be used instead.

Python Array with Examples

In this Python tutorial, we will discuss what is an array in Python and how to use lists as an array. We will also create an array by importing an array module in Python, and also we will see some examples.

• Arrays in python
• Access elements from Arrays python
• Python Array update element
• Length of an Array in python
• Add Array elements in python
• Delete Array elements in python
• Loop in Array elements in python
• What is an array module in python
• Create a python Array
• Accessing Array elements in python
• Append item in array python
• Insert element in array python
• Extend array in python
• Remove element from an array in python
• Remove the last element from array python
• Reverse an array python
• Python count the occurrence of an element in an array
• Convert array to list in python
• Find the index of an element in an array python
• Python update the element in an array
• Python lists vs arrays
• Python list to numpy arrays
• Python mean of an array
• Python mean of two arrays
• Minimum value of array python
• Maximum value of array python
• Python minimum value on 2d array
• Python maximum value on 2d array

Let us try to understand details on Python array with examples.

What is a Python Array?

What is a Python array? A Python array is a collection of items that are used to store multiple values of the same type together.

Example:

After writing the above code (arrays in python), Ones you will print ” food ” then the output will appear as “ [“fat”, “protein”, “vitamin”] ”. Here, we created an array containing food names.

You can refer to the below screenshot arrays in python

Access elements from Arrays python

How to access elements from Python Array? In python, to access array items refer to the index number. we will use the index operator ” [] “ for accessing items from the array.

After writing the above code (access elements from arrays python), Ones you will print ” a ” then the output will appear as “ vitamin”. Here, to access elements from arrays we use index number.

You can refer to the below screenshot access elements from arrays python.

Python Array update element

How to update an element in Python array? In python, to update elements in an array, we will reassign a new value to the specified index in which we want to update.

After writing the above code (python array update element), Ones you will print ” food ” then the output will appear as “ [“mineral”, “protein”, “vitamin”] ”. Here, we will reassign the new value to the desired index.

You can refer to the below screenshot python array update element

Length of an Array in Python

Let us check how to find length of an array in Python? In python, we will use len() method for finding the length of a given array.

After writing the above code (length of an array in python), Ones you will print ” a ” then the output will appear as “ 3 ”. Here, 3 is the length of an array by using len() method we get the length of an array.

You can refer to the below screenshot length of an array in python

Add Array elements in Python

Now, let us see how to add an element to a Python array? To add elements in a Python array, we can use append() method for adding the elements.

After writing the above code (add array elements in python), Ones you will print ” food ” then the output will appear as “[“fat”, “protein”, “vitamin”, “mineral”] ”. Here, the “mineral” is added to the list.

You can refer to the below screenshot add array elements in python

Delete Array elements in Python

How to delete an array elements in Python? In python, to delete array elements from the array we can use pop() method to delete.

After writing the above code (delete array elements in python), Ones you will print ” food ” then the output will appear as “[“protein”, “vitamin”] ”. Here, the pop() method will delete “fat” from the array.

You can refer to the below screenshot delete array elements in python

Loop in Array elements in Python

Let us now discuss how to loop through array elements in Python?

In python, the for loop is used to iterate through all the elements present in array.

After writing the above code (loop in array elements in python), Ones you will print ” a ” then the output will appear as ” fat protein vitamin ”. Here, the loop will iterate through all the elements in the array.

You can refer to the below screenshot loop in array elements in python

What is an array module in Python

Now, let us understand what is an array module in Python? An array is a data structure that is used to store values of the same data type. To use array in python we need to import the standard array module which gives us an object to denote an array. Here is how you can import an array module in python.

Example:

Once you have imported the array module, you can declare an array.

Create a Python Array

Let us now see how to create an array in Python?

We need to import the array module for creating an array of numeric values in python. Here, we created an array of integer type. The letter ‘i’ is used as type code to represent the integer type of array.

Example:

After writing the above code (create a python Array), Ones you will print ” a ” then the output will appear as ” array(‘i’, [10, 11, 12, 13]) ”. Here, we created an array of integer type.

You can refer to the below screenshot create a python Array.

Accessing Array elements in Python

To access array items refer to the index number in python. we will use the index for accessing items from the array and the index starts from ‘0’.

Example:

After writing the above code (accessing Array elements in python), Ones you will print ” a[2] ” then the output will appear as ” 12 ”. Here, to access elements from arrays we use the index number to access elements.

You can refer to the below screenshot accessing Array elements in python.

This is how we can access an element from a Python array.

Append item in array Python

Now, let us see how to append an item to a Python array?

To add element in an existing array we can use append() method for adding the elements in python.

Example:

After writing the above code (append item in array python), Ones you will print ” a ” then the output will appear as “ array(‘i’, [10,11,12,13,14]) ”. Here, the item ” 14 ” was appended to the existing array values.

You can refer to the below screenshot append item in array python.

Insert element in array Python

Now, let us see how to insert an element in a Python array? In Python, to insert value at any index of the array we will use the insert() method. Here, the first argument is for the index, and the second argument is for value.

Example:

After writing the above code (insert an element in array python), Ones you will print ” a ” then the output will appear as “ array(‘i’,[9, 10, 11, 12, 13]) ”. Here, the value ” 9 ” is inserted at index ” 0 ” by using the insert() method.

You can refer to the below screenshot insert element in array python.

Extend array in Python

In python, an array value can be extended with more than one value by using extend() method.

Example:

After writing the above code (extend array in python), Ones you will print ” my_array1 ” then the output will appear as “ array(‘i’,[10, 11, 12, 13, 14, 15, 16, 17]) ”. Here, we are extending more than one value in the array by using the extend() method in python.

You can refer to the below screenshot extend array in python.

Remove element from an array in Python

Now, let us see how to remove an element from an array in Python? In Python, to remove an array element we can use the remove() method and it will remove the specified element from the array.

Example:

After writing the above code (remove an element from an array in python), Ones you will print ”my_array” then the output will appear as “ array(‘i’, [10, 11, 13]) ”. Here, the remove() method will remove the “12” from the array.

You can refer to the below screenshot remove an element from an array in python.

Remove the last element from Python array

Let us see how to remove the last element from a Python array? To remove the last element from an array we can use the pop() method and it will remove the last element from the array python.

Example:

After writing the above code (remove the last element from array python), Ones you will print ”my_array” then the output will appear as “ array(‘i’, [10, 11, 12]) ”. Here, the pop() method will pop out the element “13” from the array.

You can refer to the below screenshot remove the last element from array python.

Reverse an array in Python

Let us discuss how to reverse an array in Python? In python, to reverse an array we will use the reverse() method and it will reverse all the element present in array.

Example:

After writing the above code (reverse an array python), Ones you will print ”my_array” then the output will appear as “ array(‘i’, [13, 12, 11, 10]) ”. Here, the reverse() method will reverse the element of an array.

You can refer to the below screenshot reverse an array python.

Python count occurrence of an element in an array

How to count the occurrence of an element in a Python array? To count the occurrence of an element we will use count() and it will return the number of times an element appears in an array.

Example:

After writing the above code (python count the occurrence of an element in an array), Ones you will print ”a” then the output will appear as “ 2 ”. Here, the count() method will return the number of times the element appears, and here ’12’ occurred ‘2’ times.

You can refer to the below screenshot python count the occurrence of an element in an array.

Convert array to list in Python

How to convert array to a list in Python? To convert array to list in Python, we will use tolist() method and it will convert the array to list object.

Example:

After writing the above code (convert array to list in python), Ones you will print ”a” then the output will appear as “ [10, 11, 12, 13] ”. Here, the tolist() method will convert my array to a list.

You can refer to the below screenshot convert array to list in python.

Find index of an element in an array Python

How to Find the index of an element in a Python array? To find the index of an element we will use the python in-built index() method to search the index of a specified value from the array.

Example:

After writing the above code (find the index of an element in an array python), Ones you will print ”my_array.index(12)” then the output will appear as “ 2 ”. Here, the index() method will return the index of that specified value.

You can refer to the below screenshot find the index of an element in an array python.

Python update the element in an array

How to update an array element in Python? In python, to update the element in the array at the given index we will reassign a new value to the specified index which we want to update, and the for loop is used to iterate the value.

Example:

After writing the above code (python update the element in an array), Ones you will print ”a” then the output will appear as “ 10 20 12 13 ”. Here, we reassign the new value to the index ‘1’ and it is updated with value ’20’ in an array.

You can refer to the below screenshot python update the element in an array.

Python lists vs arrays

Python mean of an array

Now, let us see mean of an array in python.

We will use numpy.mean() for the given data of an array. The function is used to compute the arithmetic mean. The function will return the average of the array element.

Example:

After writing the above code (python mean of an array), Ones you will print ”np.mean(my_array)” then the output will appear as “ array: [12, 4, 2, 7] Mean of an array: 6.25”. Here, the numpy.mean(my_arr) takes the array and returns the mean of the array.

You can refer to the below screenshot python mean of an array.

Python mean of two arrays

We will use numpy.mean() for the given data of two arrays. The function is used to compute the arithmetic mean. The function will return the average of the two arrays element.

Example:

After writing the above code (python mean of two arrays), Ones you will print ”np.mean(my_arr)” then the output will appear as “ 7.0 ”. Here, the numpy.mean(my_arr) takes the array and returns the mean of the two arrays. The arithmetic mean is the sum of the element divided by the number of elements.

You can refer to the below screenshot for python mean of two array.

Minimum value of array python

First, we will import numpy, and then we will create an array. To find the minimum value from the array we will use the “numpy.min(my_arr)” function.

Example:

After writing the above code (minimum value of array python), Ones you will print “min_element” then the output will appear as “Minimum element in the array is: 1”. Here, the numpy.min(my_arr) will return the minimum value from the array.

You can refer to the below screenshot for minimum value of array python.

Maximum value of array python

First, we will import numpy, and then we will create an array. To find the maximum value from the array we will use the “numpy.max(my_arr)” function.

Example:

After writing the above code (maximum value of array python), Ones you will print “max_element” then the output will appear as “Maximum element in the array is: 10”. Here, the numpy.max(my_arr) will return the maximum value from the array.

You can refer to the below screenshot for maximum value of array python.

Python minimum value on 2d array

First, we will import numpy, and then we will create a 2d array. To find the minimum value from the two-dimensional array we will use the “numpy.min(my_arr)” function.

Example:

After writing the above code (python minimum value on 2d array), Ones you will print “min_element” then the output will appear as “Minimum element on 2d array is: 3”. Here, the numpy.min(my_arr) will return the minimum value from the 2d array.

You can refer to the below screenshot for python minimum value on 2d array.

Python maximum value on 2d array

First, we will import numpy, and then we will create a 2d array. To find the maximum value from the two-dimensional array we will use the “numpy.max(my_arr)” function.

Example:

After writing the above code (python maximum value on 2d array), Ones you will print “max_element” then the output will appear as “Maximum element on 2d array is: 80”. Here, the numpy.max(my_arr) will return the maximum value from the 2d array.

You can refer to the below screenshot for python maximum value on 2d array

You may like the following Python tutorials:

In this Python tutorial, we learned about python arrays and also how to use it like:

• What is an Array in Python
• Access elements from Arrays python
• How to update am element in Python Array
• How to get Length of an Array in python
• How to Add Array elements in python
• Delete Array elements in python
• Loop in Array elements in python
• What is an array module in python
• Create a python Array
• Accessing Array elements in python
• Append item in array python
• How to Insert element in array python
• Extend array in python
• Remove element from an array in python
• How to remove the last element from a Python array
• Reverse an array python
• Python count the occurrence of an element in an array
• Convert array to list in python
• Find the index of an element in an array python
• How to update the element in an array in Python
• Python lists vs arrays
• Python list to numpy arrays
• Python mean of an array
• Python mean of two arrays
• Minimum value of array python
• Maximum value of array python
• Python minimum value on 2d array
• Python maximum value on 2d array

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