Most programs are interactive, meaning they allow users to provide data while the program is running. Instead of using fixed values, a program can ask the user to enter information such as their name, age, salary, or marks.

Python provides the built-in input() function to read data from the keyboard.

The input() function always waits for the user to type something and press the Enter key.

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Syntax #

input(prompt)

Parameter #

Parameter	Description
prompt	An optional message displayed before waiting for user input.

Return Value #

The input() function always returns the entered value as a string (str), regardless of what the user types.

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Example 1: Reading Input Without a Prompt #

main.py

name = input()

print(name)

Sample Input #

Alice

Output #

Alice

Explanation #

• input() waits for the user to enter data.
• The user types Alice and presses the Enter key.
• The entered text is stored in the variable name.
• print(name) displays the value stored in the variable.

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Example 2: Reading Input With a Prompt #

main.py

name = input("Enter your name: ")

print("Welcome", name)

Sample Input #

Enter your name: Alice

Output #

Welcome Alice

Explanation #

• The string "Enter your name: " is displayed before waiting for input.
• The user enters Alice.
• The entered value is stored in the variable name.
• The print() function displays a welcome message along with the entered name.

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Example 3: Reading an Integer #

main.py

age = int(input("Enter your age: "))

print(age)

Sample Input #

Enter your age: 25

Output #

25

Explanation #

• input() always returns a string.
• The int() function converts the string into an integer.
• The converted value is stored in the variable age.
• Since age is now an integer, it can be used for mathematical calculations.

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Example 4: Reading a Floating-Point Number #

main.py

salary = float(input("Enter your salary: "))

print(salary)

Sample Input #

Enter your salary: 35000.75

Output #

35000.75

Explanation #

• float() converts the entered string into a floating-point number.
• Floating-point numbers are used to represent values containing a decimal point.
• The converted value is stored in the variable salary.

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Example 5: Reading Multiple Values #

main.py

first_name, last_name = input("Enter your full name: ").split()

print(first_name)
print(last_name)

Sample Input #

Enter your full name: John Smith

Output #

John
Smith

Explanation #

• input() reads the entire line entered by the user.
• .split() divides the string into separate parts using spaces.
• The first word is assigned to first_name.
• The second word is assigned to last_name.

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Example 6: Reading Multiple Integers #

main.py

a, b = map(int, input("Enter two numbers: ").split())

print(a)
print(b)

Sample Input #

Enter two numbers: 10 20

Output #

10
20

Explanation #

• input() reads the entire line.
• .split() separates the values based on spaces.
• map(int, ...) converts every value into an integer.
• The converted integers are assigned to a and b.

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Example 7: Reading a List of Integers #

main.py

numbers = list(map(int, input("Enter numbers: ").split()))

print(numbers)

Sample Input #

Enter numbers: 10 20 30 40 50

Output #

[10, 20, 30, 40, 50]

Explanation #

• The user enters multiple numbers separated by spaces.
• .split() converts the input into a list of strings.
• map(int, ...) converts each string into an integer.
• list() converts the result into a Python list.

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Example 8: Reading a Sentence #

main.py

sentence = input("Enter a sentence: ")

print(sentence)

Sample Input #

Enter a sentence: Python is easy to learn.

Output #

Python is easy to learn.

Explanation #

• input() reads the complete line entered by the user.
• Spaces are preserved.
• The entire sentence is stored as a single string.

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Example 9: Reading a Single Character #

main.py

ch = input("Enter a character: ")[0]

print(ch)

Sample Input #

Enter a character: Apple

Output #

A

Explanation #

• input() reads the complete string entered by the user.
• [0] accesses the first character of the string.
• Even if multiple characters are entered, only the first one is stored.

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Example 10: Verifying the Return Type of input() #

main.py

value = input("Enter any value: ")

print(type(value))

Sample Input #

Enter any value: 100

Output #

<class 'str'>

Explanation #

• Even though the user entered a number, input() returns a string.
• The type() function displays the data type of a variable.
• This is why type conversion using int() or float() is often required.

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Common Mistakes #

1. Assuming input() Returns an Integer #

Incorrect

age = input("Enter your age: ")

print(age + 5)

Sample Input #

25

Output #

TypeError: can only concatenate str (not "int") to str

Reason

input() returns a string, so Python cannot add an integer to it.

Correct

age = int(input("Enter your age: "))

print(age + 5)

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2. Forgetting to Use .split() #

Incorrect

a, b = input()

Sample Input #

10 20

Output #

ValueError: too many values to unpack

Reason

Without .split(), the entire input is treated as one string instead of two separate values.

Correct

a, b = input().split()

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3. Entering Non-Numeric Data for int() #

Incorrect Input

age = int(input("Enter age: "))

Sample Input #

abc

Output #

ValueError: invalid literal for int() with base 10: 'abc'

Reason

The entered text cannot be converted into an integer.

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4. Accessing the First Character of an Empty String #

Incorrect

ch = input()[0]

Sample Input #

(User presses Enter without typing anything.)

Output #

IndexError: string index out of range

Reason

The input string is empty, so there is no first character.

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Key Points to Remember #

• input() is the built-in function used to read keyboard input.
• The prompt parameter is optional.
• input() always returns a string.
• Use int() to convert input into an integer.
• Use float() to convert input into a floating-point number.
• Use .split() to read multiple values from one line.
• Use map() to convert multiple input values into another data type.
• A single character can be obtained using string indexing.
• Always validate user input in real-world applications.