inputfunction.md

Python Input Function Guide

1. Basic Input (input())

The input() function reads input from the user as a string.

name = input("Enter your name: ")
print("Hello,", name)

Example Output:

Enter your name: John
Hello, John

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2. Getting Integer Input (int())

If you need a number, you must convert the input to an integer using int().

age = int(input("Enter your age: "))
print("Your age is:", age)

Example Output:

Enter your age: 25
Your age is: 25

💡 Important: If the user enters a non-integer value (like "abc"), it will cause an error. You can handle this using exception handling (explained later).

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3. Getting Float Input (float())

For decimal values, use float().

price = float(input("Enter the product price: "))
print("Price entered:", price)

Example Output:

Enter the product price: 12.50
Price entered: 12.5

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4. Getting Multiple Inputs in One Line

If you want multiple inputs at once, you can use split().

x, y = input("Enter two numbers separated by space: ").split()
x, y = int(x), int(y)
print("Sum:", x + y)

Example Output:

Enter two numbers separated by space: 10 20
Sum: 30

📝 Explanation:

• split() splits the input into a list based on spaces.
• You can convert each input to int() or float().

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5. Getting List Input

If you need a list of numbers:

numbers = list(map(int, input("Enter numbers separated by space: ").split()))
print("Numbers:", numbers)

Example Output:

Enter numbers separated by space: 1 2 3 4 5
Numbers: [1, 2, 3, 4, 5]

📝 Explanation:

• split() converts input into a list of strings.
• map(int, …) converts each string to an integer.
• list() creates the final list.

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6. Handling Errors with Try-Except

To prevent crashes from invalid input, use exception handling.

try:
    age = int(input("Enter your age: "))
    print("Your age is:", age)
except ValueError:
    print("Invalid input! Please enter a valid number.")

Example Output (if invalid input is given):

Enter your age: abc
Invalid input! Please enter a valid number.

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7. Taking Input Until a Condition is Met (while Loop)

while True:
    number = input("Enter a number (or type 'exit' to stop): ")
    if number.lower() == 'exit':
        break
    try:
        number = int(number)
        print("You entered:", number)
    except ValueError:
        print("Invalid input, please enter a number.")

Example Output:

Enter a number (or type 'exit' to stop): 10
You entered: 10
Enter a number (or type 'exit' to stop): abc
Invalid input, please enter a number.
Enter a number (or type 'exit' to stop): exit

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8. Reading Input with sys.stdin.readline()

For faster input in competitive programming:

import sys
name = sys.stdin.readline().strip()
print("Hello,", name)

🚀 Advantage: Works faster for large inputs compared to input(). 💡 Use .strip() to remove extra newlines.

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9. Taking Multi-Line Input

lines = []
print("Enter multiple lines (type 'STOP' to end):")
while True:
    line = input()
    if line == "STOP":
        break
    lines.append(line)
print("You entered:\n", "\n".join(lines))

Example Output:

Enter multiple lines (type 'STOP' to end):
Hello
How are you?
STOP
You entered:
Hello
How are you?

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10. Taking Dictionary Input

keys = input("Enter keys separated by space: ").split()
values = input("Enter values separated by space: ").split()
dictionary = dict(zip(keys, values))
print("Dictionary:", dictionary)

Example Output:

Enter keys separated by space: name age city
Enter values separated by space: John 25 London
Dictionary: {'name': 'John', 'age': '25', 'city': 'London'}

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📌 Summary of Input Methods

Method	Description
input()	Reads input as a string.
int(input())	Reads an integer input.
float(input())	Reads a float input.
split()	Splits input into a list of words.
map(int, input().split())	Converts multiple inputs to integers.
sys.stdin.readline()	Faster input reading for large inputs.
while True:	Repeated input until a condition is met.
try-except	Handles invalid input errors.
dict(zip(keys, values))	Creates a dictionary from input.

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