Hướng dẫn array string python example

While working with python data types, there are situations when you want to convert the data collected from one type to another. There are 4 methods by which we can convert a list to a string in python with fewer lines of code. These methods of converting a list into a string include iteration, comprehension, join(), and map() method. But before understanding all these conversion methods in detail, let us understand what are lists and strings.

Nội dung chính

• What is a List? 
• What is a String?
• Convert List to String in Python
• 1) Iterating through the List
• 2) Using join() method
• 3) Using List Comprehension
• 4) Using map() function
• Introduction to String Array in Python
• Accessing of Elements
• Lists of String Array in Python
• Methods of String Array in Python
• Recommended Articles

Nội dung chính

• What is a List? 
• What is a String?
• Convert List to String in Python
• 1) Iterating through the List
• 2) Using join() method
• 3) Using List Comprehension
• 4) Using map() function
• Introduction to String Array in Python
• Accessing of Elements
• Lists of String Array in Python
• Methods of String Array in Python
• Recommended Articles
• Video liên quan

What is a List? 

The list is one of the most important data types in the python language. A python list is an ordered and changeable collection of data objects. In Python language, the list is written as commas separated values inside the square bracket. It can also contain duplicate elements along with the negative indexing elements. The important advantage of the list is that the elements inside the list are not compulsory to be of the same data type. List undergo the operations like slicing, concentrating, etc., just like the string operations. Also, you can create a nested list, i.e., a list containing another list.

Example

sam_list = [10,"favtutor",["compile","it"]] print(sam_list)

Output:

[10, 'favtutor', ['compile', 'it']]

What is a String?

A string is defined as a sequence of characters where a character is a simple symbol. For example, in the English Language, we have 26 characters available. The computer system does not understand characters therefore, it deals with binary numbers. Even though we can see characters on our monitor screens, internally it is stored and manipulated internally as a combination of 0's and 1's. In the Python programming language, a string is a sequence of Unicode characters. It s an immutable sequence data type wrapped inside single or double-quotes. That means that once you define a string, you cannot change it.

You can also assign a multi-line string to a variable using triple quotes. Many string manipulation methods are available for string data types like join(), split(), concatenation, etc. However, this method does not modify the original strings but creates a copy and modifies them accordingly.

Example

a = "Compile With Favtutor" print(a)

Output

Convert List to String in Python

As mentioned earlier, there are 4 methods to convert a list to string in python. Let us study them one by one in detail, along with the example and corresponding output. 

1) Iterating through the List

This method will iterate every index of the input list one by one and add it to the empty string. 

Example

# converting list to string using iteration def listToString(s): # initialize an empty string string = "" # traverse in the string for element in s: string += element # return string return string # Driver code s = ['Compile ', 'With ', 'Favtutor '] print(listToString(s))

Output:

2) Using join() method

Every element of the list will be traversed and added to the empty string. Join() method is used to concatenate all these elements and form the final output. This method will fail to work if the list contains integer elements, and therefore the output will be TypeError Exception. 

Example

# converting list to string using join() method # Function to convert def listToString(s): # initialize an empty string string = " " # return string return (string.join(s)) # Driver code s = ['Compile ', 'With ', 'Favtutor'] print(listToString(s))

Output:

3) Using List Comprehension

As mentioned earlier, the join() method will fail to work if you have integer elements in your input list. But to overcome this failure, you can use the List comprehension along with join() method. List comprehension will help you to create a list of elements from the existing input list. And later uses a for loop to traverse the elements by element-wise patterns. After the traversal of elements by list comprehension, you can use the join() method to concatenate the traversed elements of the list into an empty string. 

Example

# converting list to string using list comprehension s = ['Compile', 'With', 'Favtutor'] # using list comprehension listToStr = ' '.join([str(element) for element in s]) print(listToStr)

Output:

4) Using map() function

map() function accepts the iterable objects such as tuples, lists, or strings. Hence, it is used to map the elements of the iterable objects with the function provided. 

Example

# converting list to string using map() function s = ['Compile', 'With', 'Favtutor'] # using list comprehension listToStr = ' '.join(map(str, s)) print(listToStr)

Output:

Conclusion

List and string have their own importance as a data type in python. This article referred to python lists and strings in detail, along with different techniques and methods to convert list data types into strings. It is highly recommended to learn and understand all these methods in detail as they are very effective and efficient for converting the list to string using fewer lines of code. 

Introduction to 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.

Code:

Output:

2. Accessing by Index

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

Code:

Output:

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.

Code:

Output:

4. Length

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

Code:

Output:

5. Looping

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

Code:

Output:

6. Appending

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

Code:

Output:

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.

Code:

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.

Code:

Output:

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.

Code:

Output:

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.

Code:

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.

Code:

Output:

3. count()

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

Code:

Output:

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.

Code:

Output:

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:

Code:

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.

Code:

Output:

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.

Code:

Output:

7. reverse()

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

Code:

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.

Code:

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, 2nd and 3rd 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.

Code:

Output:

10. Change of the item value

The value of a specific item can be changed.

Code

Output:

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.

Code:

Output:

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 (( )).

Code:

Output:

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 –

1. Loops in Python
2. 2D Arrays In Python
3. String Array in C++
4. String Array in C#