Linux Hint Posted October 6, 2020 Share Posted October 6, 2020 A Python variable is a location in memory to store the values. The variables are reserved memory locations. A variable is a bag or container that stores the value. We store our data in a Python variable which is subsequently used for multiple purposes i.e. processing, value printing, etc. Every value that is assigned to a variable has a data type. Following are the different types in Python: Numbers Strings Dictionary List Tuple In Python, the variables can be declared by alphabet or by name. There should not be a special symbol like ‘!@&’ in the variable name. The variable name cannot start with the digit and full stop. According to the coding ethics and rules, the name of the variable should begin with an alphabet or underscore (_). In this article, we will see that How to declare and assign a value to a variable. How to use a variable. Replace or change the variable value. Python strings Concatenation. Assign multiple values to variables Constants. Different standard data type examples. Delete variable. How to declare and assign a value to a variable The Python variables are declared and assigned like this: Price = 100 Here, the price is the variable name, and 100 is the variable value. When the variable is declared space is reserved in memory automatically. The = operator is used to initialize the variable with a value. The operand on the left side of the = operator is variable and the operand on the right side of the = operator is value. Let’s declare another variable and calculate the sum of the two numbers. In this case, we will declare two variables and assign them value. number_1 = 10 number_2 = 20 The number_1 and number_2 are the names of the variables whereas, the 10 and 20 are the values assigned to variables respectively. In a Python program, we can have multiple types of variables i.e. integer, float, string, and list. # Assigning string value to the variable name = "Kamran"# Assigning integer value to the variable age = 25# Assigning float value to the variable weight = 65.7# Assigning a list to the variable courses = ["Python", "Linux Kernel Development", "MySQL Database", "C++ Data Structure"] How to use a variable The variable is used for various purposes i.e. By using the variable name, we can print the value which is assigned to a particular variable, we can use the variable for performing calculations, and we can also use the variable for processing. Let’s consider the number examples and calculate the sum of two variables. We will declare two numbers of variables and assign value to them. After, that we will declare a sum variable, and store the sum value in this variable. Lastly, we will print the sum variable. # Declaring a variable number_1 and assigning the value number_1 = 10# Declaring a variable number_2 and assigning the value number_2 = 20# Declaring a sum variable and taking the sum of two numberssum = number_1 + number_2#printing the sum valueprint("The sum value is: ",sum) Output The output is displayed on the Python console. The sum value is printed using the “sum” variable. Let’s see another example of variables. # a name variable name = "Kamran"# printing the name variableprint(name)# a webiste variable website = "LinuxHint"# printing the website nameprint(website)# an age variable age = 25# printing the age valueprint(age)# a variable for storing weight value weight = 65.7# printing the weight valueprint(weight)# a laptop variable laptop = "HP Folio 9470m"# printing the laptop nameprint(laptop)# an operating system variable operating_system = "Ubuntu 20.04"# printing the laptop nameprint(operating_system)# a list of courses courses = ["Python", "Linux Kernel Development", "MySQL Database", "C++ Data Structure"]# printing the list of coursesprint(courses) Output The output is displayed on the Python console. Replace or change the variable value The variable is like a bag. It stores the data or variable value. The data in the bag could be replaced at any time. It means that we can easily replace the value of the variable at any time. Let’s see an example of replacing or changing the value of a variable. We declare a ‘company’ variable and assign a value. Later on, we use this variable again and assign another value. So, the first value will be replaced and the second value will be stored in the variable. # declaring a company variable and assigning the value company = "Microsoft"print(company)# Assigning a new value to the company variable company = "Apple Inc."print("The replaced value is:", company) Output The output is displayed on the Python console. Similarly, we can replace the integer, float, complex number, list, etc. value in this way. # declaring a number variable and assigning the value number = 10print(number)# Assigning a new value to the number variable number = 20print("The replaced value is:", number)# declaring a float variable and assigning the value float_number = 10.1print(float_number)# Assigning a new value to the float variable float_number = 20.04print("The replaced value is:", float_number)# declaring a complex number variable and assigning the value complex_number = 2+3jprint(complex_number)# Assigning a new value to the complex number variable complex_number = 5+3jprint("The replaced value is:", complex_number)# declaring a list variable and assigning the value name_list = ["Ali", "Kamran", "Talha"]print(name_list)# Assigning a new value to the list variable name_list = ["Umer", "Usman", "Assad"]print("The replaced value is:", name_list) Output The output is displayed on the Python console. Python strings Concatenation Strings in Python are the set of characters. Strings are represented inside a quotation mark. The string represents a single character, word, or a complete sentence. In Python, we can concatenate or combine the Strings by the “+” operator. Let’s see an example of this. In the given example, we have one variable which contains some string value. Moreover, we have another variable that contains another string value. Lastly, we have concatenated both strings using the “+” operator. # Declaring one string variable and assigning a value text = "Hello everyone."# Declaring second string variable and assigning the value text_web = " Welcome to the LinuxHint"# Concatenating the strings using "+"print(text+text_web) Output The output is displayed on the Python console. We can do similar work in this way and we will get the same output. # Declaring one string variable and assigning the value text = "Hello everyone."# Concetenating the strings using "+"print(text+" Weclome to LinuxHint") Output Assign multiple values to variables In Python, multiple values can be assigned to multiple variables simultaneously. We can also assign an atomic value to numerous variables at one time. For example num1 = num2 = num3 = 5 Here, all three variables (num1, num2, num3) are assigned to a single value 5. If we print all these three variables, you can see that the value of all these three variables is the same. num1 = num2 = num3 = 5print(num1)print(num2)print(num3) Output You can also assign multiple values to multiple variables like this: # Assigning values to three variables age,rollNumber,name = 25,12,"Kamran"#print age valueprint(age)# print roll number valueprint(rollNumber)# print name valueprint(name) In the above-given example, we have two integer objects, age and roll number, and one string object. All the variables are created and initialized in a line. In the output, you can see that all the values are successfully assigned to all the variables. Output Constants Constants are those variables whose values cannot change. The constant value always remains the same. We use multiple constants in mathematics and physics like the value of PI and Gravity value. In python, the constants are written in the capital letters like this: # Declaring a constant for PI PI = 3.14# Declaring a constant for Foiass FOIASS= 1.18 Different standard data type examples As we discussed previously, Python has multiple different data types like numbers, strings, lists, tuple, and dictionaries. We have discussed the numbers and strings in detail. Now, let’s see the examples of lists, tuples, and dictionaries. Python list A list in Python contains various comma-separated items. A list can contain the heterogeneous type of items. The list values are accessed by the []. We specify the index number inside the slice operator ([]). The index number starts from zero. For example: # Declaring a student list student_list = ["Ali",1, "Kamran",2, "Talha",3]#printing the student listprint(student_list)#print first element of listprint(student_list[0])#print second element of listprint(student_list[1])#print third element of listprint(student_list[2])#print fourth element of listprint(student_list[3])#print fifth element of listprint(student_list[4])#print sixth element of the listprint(student_list[5]) Output The output is following Python tuple Tuples are another type of data type in Python. Tuples are similar to the Python list. The main difference between tuples and the Python list is that the Python tuples are declared inside the parenthesis (). Following is the Python tuple example: # Declaring a student tuple student_tuple= ("Ali",1, "Kamran",2, "Talha",3)# printing the student tupleprint(student_tuple)# print first element of tupleprint(student_tuple[0])# print second element of tupleprint(student_tuple[1])# print element of tuple starting from the 3rd elementprint(student_tuple[2:])# print element of tuple starting from the 2nd 6th elementprint(student_tuple[1:5])# print fifth element of tupleprint(student_tuple[4])# print sixth element of tupleprint(student_tuple[5]) Output The output is displayed on the Python console. Python Dictionary Python dictionaries work like the hash table. A Python dictionary is alike a key-value pair. A dictionary is declared using the set of curly braces ({}). When we declare the key-value pair, we access the value by using the key. We pass the key as an argument and the value is returned as a result. Let’s create a Python dictionary for a student. # Declaring a student dictionary student_dict = {'name': 'Kamran','age':25, 'class': 'MSSE'}# Printing the name of student by using name keyprint(student_dict['name'])# Printing the age of student by using the age keyprint(student_dict['age'])# Printing the class of student by using the class keyprint(student_dict['class']) Output The output is displayed on the Python console. Delete variable We can delete a variable in Python and remove it from the memory by using the del keyword. So, if we print the variable or use the variable after deleting it, the compiler will return an error. # Declaring a name variable name = "Kamran"# print the name variableprint(name)# deleting the name variabledel name# printing the name variable after deleting itprint(name) Output The output is displayed on the Python console. In the output, you can see that the compiler returns an error “The variable name is not defined”. Conclusion The Python variables are like a container or bag that store the values. Variables are declared by names or alphabets. We can easily replace the Python variable values and assign value to multiple variables simultaneously. There are different data types in Python. In this article, we have explained the variables and different data types with several examples. We have used Python 3 syntax throughout this article. View the full article Quote Link to comment Share on other sites More sharing options...
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