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variables in Python

A Beginner’s Guide To Python Variables and Types

Variables in Python

Variables is a place placeholders used to contain a value, character number, etc. We use a name for our variable as a, b, number, etc. When we declare a variable, it will reserve a memory location we can use any name for our variable except reserve words.

Numeric type Variables

Integers (int) and floats (float) are numeric types in Python, these type of variables holds numbers. You can perform mathematical operations with them. The Python interpreter can then evaluate these expressions to produce numeric values.

You can use the type() function to return the type of a value of a variable.

Examples:

Code

Integer assignment

counter = 100
print(counter)
Python
100

Floating Point Numbers

Code

Assign Float Value

des_value = 10.12 
print(des_value)
Python
10.12

Print Value of Variables in Python

Code

var1 = "Hello, Python"
print(var1)
Python
Hello, Python

We can also assign other type of values as:

Code

var2 = 4
var3 = 36.9
print(var2, var3)
Python
4 36.9

Note: Commas in the print function will show a space in the output.

We can also assign multiple values to multiple variables at the same time as:

Code

a, b, c = 1, 2, 'John'
Python

We can also check the type of a variable by using the type keyword:

Code

a = 5
print(type(a))
Python
<class 'int'>

Strings in Python

The string is a combination of characters we can use string literals surrounded by single or double quotes such as ‘Hello Python’ OR “Hello Python”.

For displaying literals by using the print () function.

Code

Assign String Value

 name = "John"
print(name)
Python
John

Code

# Example: Print 'Hello Python'
print('Hello Python')
print("Hello Python")  # Corrected the casing of 'Print'

# Assign String to a Variable
a = "Hello"  # Corrected the indentation and casing of 'Print'
print(a)
Python
Output:
Hello Python
Hello Python
Hello

Multiline Strings

We can also print a multiline string to a variable by using three quotes:

Code

a = """Python is an open-source programming language created by Dutch programmer Guido van Rossum, named after the British sketch comedy group Monty. Python is a high-level programming language, with applications in numerous areas, including web programming, scripting, data analysis and artificial intelligence."""
print(a)
Python
Output:
Python is an open-source programming language created by Dutch programmer Guido van Rossum, named after the British sketch comedy group Monty. Python is a high-level programming language, with applications in numerous areas, including web programming, scripting, data analysis and artificial intelligence.

We can also store a string in an array and get the input by using the index value of a single character as:

Code

a = "Hello, Python!"
print(a[1])
Python
Output:
e

Note: This will print the character at index 1 of the string a, which is e. Remember that Python uses 0-based indexing, so the first character is at index 0.

String Slicing

As we know string is a combination of characters. If you have a huge document of about 10000 words and you just want to pick some lines to write from this document then Python provides this facility which is called “string slicing”.

Print the characters from index 3 to index 11:

Code

b = "Hello, Python!"
print(b[3:11])
Python
Output:
lo, Pyt

We can also print a string by skipping one character:

Code

b = "Hello, Python!"
print(b[3:11:2])     
Python
Output:
l,pt

Python String Negative Indexing

Code

b = "Hello, Python!"
print(b[-5:-2])
Python
Output:
tho

String Methods

Python provides some built-in methods to use on strings these methods are also called string methods.

 Length Method

We can get the length of a string by using the len () function.

Code

b = "Hello Python!"
print(len(b))
Python
Output:
13

Type Method

Example:

Python strip () method is used to remove whitespaces from the beginning and the end.

Code

The strip() method removes leading and trailing white-space characters (spaces, tabs, newlines) from the string b. Since there are no leading or trailing white-space characters in the string "Hello Python!", the output remains unchanged.

   b = "Hello Python!" 
print(b.strip())
Python
Hello Python!

Upper Method

Python’s upper () method converts the whole string into upper-case letters.

Code

  b = "Hello Python!" 
print(b.upper())  
Python
Output:
HELLO PYTHON!

Explanation: The upper() method converts all characters in the string b to uppercase, resulting in the output "HELLO PYTHON!".

Lower Method

Python lower () method converts the whole string into lowercase letters.

Code

b = "Hello Python!" 
print(b.lower())
Python
Output:
hello python!

Explanation: The lower() method converts all characters in the string b to lowercase, resulting in the output "hello python!".

Replace Method

Python replace () method replaces a string with another string.

Code

b = "Hello Python!" 
print(b.replace("H", "J"))
Python
Output:
Jello Python!

Explanation: The replace() method replaces all occurrences of the sub-string "H" with the sub-string "J" in the string b, resulting in the output "Jello Python!".

Split Method

Python split () method converts the whole string into upper case letters.

Code

b = "Hello Python!" 
print(b.split(" "))
Python
Output:
[‘Hello’, ‘Python!’]

In or Not in Method (check string)

You can use in or not-in built-in methods to check if a phrase is present in a string or not. The output will be True or False.

Code

b = "A quick brown fox jumps over the lazy dog."
x = "jumps" in b
print(x)
Python
Output:
True

String Concatenation

Strings can be concatenated in Python by using the + operator.

Concatenate variable a with variable b.

Code

a = "Hello" 
b = "Python"
c = a + b
print(c)
Python
Output:
HelloPython

Explanation: The variables a and b store the strings “Hello” and “Python” respectively. The expression a + b concatenates these strings together, resulting in the string “HelloPython”, which is then printed.

Python Booleans

Boolean represent output in the form of True or False.

Boolean Values

In some cases, we need to know whether the expression is True or False.

Code

print(1 > 2)
print(1 == 2)
print(1 < 2)
Python
Output:
False
False
True

Explanation: Each print statement evaluates a comparison expression:

  • 1 > 2 is False because 1 is not greater than 2.
  • 1 == 2 is False because 1 is not equal to 2.
  • 1 < 2 is True because 1 is less than 2.

Print a message based on whether the condition is True or False:

Code

print(1 > 2)
print(1 == 2)
print(1 < 2)
Python
Output:
False
False
True

Evaluate Values and Variables

We can evaluate any value by using the bool () function, it will return True or False.

print (bool("Hello"))    
print (bool (15))
Python
Output:
True
True

Explanation: The bool() function returns True if the argument is non-empty for strings and non-zero for numeric values. In this case:

  • "Hello" is a non-empty string, so bool("Hello") evaluates to True.
  • 15 is a non-zero integer, so bool(15) evaluates to True.

Type Casting in Python

We can use the type casting technique to convert our value from one type to another type e.g we can convert a string value into an integer as we explain below:

If we want to add string values then in the output both values will be concatenated except for calculating the sum.

Without using Type Casting

Code

Var1 = "54"
Var2 = "30"
print(Var1 + Var2)
Python
Output:
5430

Explanation: The variables Var1 and Var2 store strings "54" and "30" respectively. When you use the + operator with strings, it performs concatenation rather than arithmetic addition. So, Var1 + Var2 concatenates the strings "54" and "30", resulting in "5430".

By using Type Casting

Code


Var1 = "54"
Var2 = "30"
print(int(Var1) + int(Var2))
Python
Output:
84

Explanation: In this corrected code, int(Var1) and int(Var2) convert the string variables Var1 and Var2 into integers, resulting in the numbers 54 and 30 respectively. Then, these integers are added together using the + operator, resulting in the sum 84, which is printed.

User Input

We can interact with our users by asking the user for input.

We can take input from a user by using the input () method.

Python 3.6 provides a user input method as input ()

Python 2.7 provides the user input method as raw_input ()

Code

print("Enter a number")
num = input()
print("You entered:", num)
Python
Output:
Enter a number
5
You entered: 5

Explanation: The corrected code prompts the user to enter a number with the message “Enter a number”. The input() function then waits for user input, which is stored in the variable num. Finally, it prints the message “You entered:” followed by the value stored in num.

Note: The input method stores each value as a string so if you want to add values for calculating sum then first you have to convert values into integers by using the type casting technique. 

Example:

Code

print("Enter a number")
num = input()
print("You entered:", int(num) + 10)
Python
Input:
10
Output:
Enter a number
You entered: 20

Author: TCF Editorial
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