Python array type string

array — Efficient arrays of numeric values¶

This module defines an object type which can compactly represent an array of basic values: characters, integers, floating point numbers. Arrays are sequence types and behave very much like lists, except that the type of objects stored in them is constrained. The type is specified at object creation time by using a type code, which is a single character. The following type codes are defined:

It can be 16 bits or 32 bits depending on the platform.

Changed in version 3.9: array(‘u’) now uses wchar_t as C type instead of deprecated Py_UNICODE . This change doesn’t affect its behavior because Py_UNICODE is alias of wchar_t since Python 3.3.

The actual representation of values is determined by the machine architecture (strictly speaking, by the C implementation). The actual size can be accessed through the array.itemsize attribute.

The module defines the following item:

A string with all available type codes.

The module defines the following type:

class array. array ( typecode [ , initializer ] ) ¶

A new array whose items are restricted by typecode, and initialized from the optional initializer value, which must be a list, a bytes-like object , or iterable over elements of the appropriate type.

If given a list or string, the initializer is passed to the new array’s fromlist() , frombytes() , or fromunicode() method (see below) to add initial items to the array. Otherwise, the iterable initializer is passed to the extend() method.

Array objects support the ordinary sequence operations of indexing, slicing, concatenation, and multiplication. When using slice assignment, the assigned value must be an array object with the same type code; in all other cases, TypeError is raised. Array objects also implement the buffer interface, and may be used wherever bytes-like objects are supported.

Raises an auditing event array.__new__ with arguments typecode , initializer .

The typecode character used to create the array.

The length in bytes of one array item in the internal representation.

Append a new item with value x to the end of the array.

Return a tuple (address, length) giving the current memory address and the length in elements of the buffer used to hold array’s contents. The size of the memory buffer in bytes can be computed as array.buffer_info()[1] * array.itemsize . This is occasionally useful when working with low-level (and inherently unsafe) I/O interfaces that require memory addresses, such as certain ioctl() operations. The returned numbers are valid as long as the array exists and no length-changing operations are applied to it.

When using array objects from code written in C or C++ (the only way to effectively make use of this information), it makes more sense to use the buffer interface supported by array objects. This method is maintained for backward compatibility and should be avoided in new code. The buffer interface is documented in Buffer Protocol .

“Byteswap” all items of the array. This is only supported for values which are 1, 2, 4, or 8 bytes in size; for other types of values, RuntimeError is raised. It is useful when reading data from a file written on a machine with a different byte order.

Return the number of occurrences of x in the array.

Append items from iterable to the end of the array. If iterable is another array, it must have exactly the same type code; if not, TypeError will be raised. If iterable is not an array, it must be iterable and its elements must be the right type to be appended to the array.

Appends items from the string, interpreting the string as an array of machine values (as if it had been read from a file using the fromfile() method).

New in version 3.2: fromstring() is renamed to frombytes() for clarity.

Read n items (as machine values) from the file object f and append them to the end of the array. If less than n items are available, EOFError is raised, but the items that were available are still inserted into the array.

Append items from the list. This is equivalent to for x in list: a.append(x) except that if there is a type error, the array is unchanged.

Extends this array with data from the given unicode string. The array must be a type ‘u’ array; otherwise a ValueError is raised. Use array.frombytes(unicodestring.encode(enc)) to append Unicode data to an array of some other type.

Return the smallest i such that i is the index of the first occurrence of x in the array. The optional arguments start and stop can be specified to search for x within a subsection of the array. Raise ValueError if x is not found.

Changed in version 3.10: Added optional start and stop parameters.

Insert a new item with value x in the array before position i. Negative values are treated as being relative to the end of the array.

Removes the item with the index i from the array and returns it. The optional argument defaults to -1 , so that by default the last item is removed and returned.

Remove the first occurrence of x from the array.

Reverse the order of the items in the array.

Convert the array to an array of machine values and return the bytes representation (the same sequence of bytes that would be written to a file by the tofile() method.)

New in version 3.2: tostring() is renamed to tobytes() for clarity.

Write all items (as machine values) to the file object f.

Convert the array to an ordinary list with the same items.

Convert the array to a unicode string. The array must be a type ‘u’ array; otherwise a ValueError is raised. Use array.tobytes().decode(enc) to obtain a unicode string from an array of some other type.

When an array object is printed or converted to a string, it is represented as array(typecode, initializer) . The initializer is omitted if the array is empty, otherwise it is a string if the typecode is ‘u’ , otherwise it is a list of numbers. The string is guaranteed to be able to be converted back to an array with the same type and value using eval() , so long as the array class has been imported using from array import array . Examples:

array('l') array('u', 'hello \u2641') array('l', [1, 2, 3, 4, 5]) array('d', [1.0, 2.0, 3.14]) 

Packing and unpacking of heterogeneous binary data.

Packing and unpacking of External Data Representation (XDR) data as used in some remote procedure call systems.

The NumPy package defines another array type.

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String Array in Python

String Array can be defined as the capacity of a variable to contain more than one string value at the same time, which can be called and accessed at any time in the program during the execution process. There is no pre-defined feature for character data types in Python, as every single character in python is treated as a string by itself. The various types of a string array in python are the Lists, the negative indexing, accession by index, looping, appending, the length using len() method, removing using pop() method, clear(), copy(), etc.

Accessing of Elements

Python does not have built-in support for Arrays. Python lists are used to serve the purpose, so we will look into Lists. It is to be noted that Python does not have a character data type. A single character in itself is a string with length 1. Square brackets are used to access the elements of the String.

Lists of String Array in Python

Below are the lists of a String array in Python:

1. List

When there is a need for order and a requirement of frequent change, we prefer selecting the list. Another feature of the list is it allows duplicates. Here is a simple example of a list.

2. Accessing by Index

We can even access a particular element by referring to an index.

3. Negative Indexing

We can even access indexing negatively. In this case, that last most element will have an index of -1; the second last will be -2, the third last will be -3, so on and so forth.

4. Length

We can even return the length of an array by using the len() method.

5. Looping

Looping through the array element is also an easy task. We use ‘for in’ while looping through the array.

6. Appending

If one has to append to the list, then it is possible using ‘append()’

7. Removing

Removal of any element can be done via the pop() method. Here we can be specific about the deletion of any particular element by referring to the index.

Output: As pop(1) represents the second element from the list. It is removed.

We can also use the remove() method and mention the particular element that can be removed.

Methods of String Array in Python

We have a list of underlying methods that can be used over the list and arrays. We have come across append(), pop() and remove() previously. We shall discuss here other methods that can be used.

1. clear()

This removes all the elements from the list, and it will present you with a list clear of all elements.

To remove the element from the list, we have removed the () method, a pop() method, which we have discussed. There is also a ‘del’ keyword that clears the list.

Output: The del list deletes the list, and we get the following output.

2. copy()

This method returns a copy of the list. As you can see from the example below.

3. count()

Returns to us the number of elements in the list with a specified value.

4. extend()

We add the elements to the end of the list here with the help of another list. Then the second list forms the extends the first list. Here it is how it is done.

The list has append() and extends the () method to concatenate or join two lists, but the ‘+’ operator can also perform this action. We shall see this simple join in the step below:

Output: Grocery list is the concatenated list of the above ‘fruits’ and ‘vegetables’ list.

5. index()

This method returns the position of the occurrence of the particular element.

6. insert()

This method returns the element which has to be inserted at a specified position. This method takes 2 arguments, first the index and the second, the element that has to be positioned at that index.

7. reverse()

This method reverses the sorting order of the list. This method returns a reversed iterator object.

Output: We see how the entire list is reversed here.

8. sort()

This method will arrange the list in alphabetical order, or it can also be said that it sets the list according to ascending order.

The method takes 2 parameters; one of the parameters is reversed, and the other one is key which may specify the sorting criteria. If reverse=true, then the list will be sorted in descending order, whereas if the reverse=false then ascending. The 2 parameters are optional.

Below is an example where we have used the reverse parameter.

Output: Here, we see the default sorting and, in the other, the reverse of the previous one.

9. Range of Indexes

If we need a selective list of elements from where to start and where to end, we go for this option.

Example: Suppose if we want only the 1st, 2 nd and 3 rd element of the list, then we would do the below. It is to be noted that the list begins with 0, and it does not include the last range.

10. Change of the item value

The value of a specific item can be changed.

11. Checking whether an element presents or not.

Suppose we have to check if a particular element is present or not, then use the ‘in’ keyword. Here we make use of the ‘if’ keyword to confirm the presence of an element.

12: list() constructor

There is also a list of the constructor that is used to make a new list. A good note must be taken that here square brackets are dropped [] and instead double rounded brackets are used (( )).

Conclusion

It is also to be understood that Python has no support for Array; it is still a list that we have used. However, Numpy is a library that can be used to create the 2D, 3D array and is used at computing scientific and mathematical data.

Recommended Articles

This is a guide to String Array in Python. Here we have discussed overview, accessing of elements, python list and methods with codes and outputs. You can also go through our other related articles to learn more –

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