codeIn [Spark]

Python Input and Output Functions #

Python provides various ways to handle input and output (I/O) operations. The most basic functions for these operations are print() for output and input() for taking input from the user.

1. The print() Function (Output) #

The print() function in Python is used to display output on the screen. It can print strings, numbers, variables, and even the results of expressions.

Syntax of print(): #

print(*objects, sep=' ', end='\n', file=sys.stdout, flush=False)

Parameters: #

• *objects: One or more objects to be printed. Multiple objects are separated by a space by default.
• sep: Specifies how to separate multiple objects (default is a single space ' ').
• end: Determines what to print at the end of the output (default is a newline '\n').
• file: Specifies where to send the output (default is the console sys.stdout).
• flush: If True, the output is forcibly flushed. Default is False.

Basic Example of print(): #

# Simple print statements
print("Hello, World!")  # Output: Hello, World!
print(10 + 5)           # Output: 15

2. Printing Multiple Objects #

You can pass multiple objects to print() and separate them with a space by default. You can also change the separator using the sep parameter.

Example: #

# Printing multiple objects
name = "Alice"
age = 25
print("Name:", name, "Age:", age)  # Output: Name: Alice Age: 25

# Custom separator
print("Apple", "Banana", "Cherry", sep=", ")  # Output: Apple, Banana, Cherry

3. Customizing the end Parameter #

By default, print() ends with a newline (\n). You can change the ending using the end parameter.

Example: #

# Changing end parameter
print("Hello", end=" ")
print("World!")  # Output: Hello World!

---

4. Printing to a File #

You can direct the output of print() to a file using the file parameter. By default, print() sends output to the console, but you can redirect it to a file.

Example: #

# Writing output to a file
with open("output.txt", "w") as f:
    print("This is written to the file.", file=f)

# Check the file 'output.txt' to see the output.

---

5. Using flush Parameter #

The flush parameter is used to forcefully flush the output stream. This is typically useful when printing large amounts of data or when you need real-time output.

Example: #

import time

# Flushing output
for i in range(5):
    print(i, end=' ', flush=True)  # Output: 0 1 2 3 4
    time.sleep(1)

---

6. The input() Function (Input) #

The input() function is used to take input from the user in Python. By default, input() returns the input as a string, which can be converted to other types like integers or floats if needed.

Syntax of input(): #

input([prompt])

Parameters: #

• prompt: A string that will be displayed to the user, prompting them for input. This parameter is optional.

Basic Example of input(): #

# Taking input from the user
name = input("Enter your name: ")
print("Hello", name)  # Output depends on the user's input.

7. Converting Input to Other Data Types #

The input() function always returns the input as a string. To handle numeric inputs, you need to convert the string to the desired type using int(), float(), or other type-casting functions.

Example: #

# Taking integer input
age = int(input("Enter your age: "))
print(f"Next year, you will be {age + 1} years old.")

Example: Taking Float Input #

# Taking float input
price = float(input("Enter the price of the item: "))
print(f"The price with tax is: {price * 1.05}")

8. Input and Output Together: A Simple Program #

Here’s a small program combining both input() and print():

# Taking user input and displaying it
name = input("What is your name? ")
age = int(input("How old are you? "))

print(f"Hello {name}, you are {age} years old.")

9. Advanced Usage: Multiple Inputs at Once #

In Python, you can take multiple inputs at once and split them into separate variables. The split() function can be used to achieve this.

Example: Taking Multiple Inputs in One Line #

# Taking multiple inputs
x, y = input("Enter two numbers separated by space: ").split()

print(f"First number: {x}, Second number: {y}")

You can also convert the inputs to integers or floats:

# Taking multiple integer inputs
x, y = map(int, input("Enter two numbers: ").split())
print(f"Sum: {x + y}")

10. Error Handling in Input #

When taking input from users, especially numeric input, you should handle potential errors (like entering a non-integer value) using try–except blocks.

Example: Handling Invalid Input #

try:
    num = int(input("Enter an integer: "))
    print(f"Your number is {num}")
except ValueError:
    print("That's not a valid integer.")

11. Using eval() with input() #

In certain scenarios, eval() can be used with input() to evaluate Python expressions entered by the user. Be cautious while using eval() as it can execute arbitrary code and lead to security issues.

Example: #

# Using eval() to evaluate expressions
expression = input("Enter a mathematical expression: ")
result = eval(expression)
print(f"Result: {result}")

Warning: eval() is powerful but dangerous, so use it wisely.

---

12. Formatting Output in Python #

You can format the output in Python using the following methods:

12.1. Using f-strings (Formatted String Literals) #

# Using f-strings
name = "Alice"
age = 25
print(f"Name: {name}, Age: {age}")

12.2. Using .format() Method #

# Using .format() method
print("Name: {}, Age: {}".format("Bob", 30))

12.3. Using Percentage % Formatting #

# Using % formatting
name = "Charlie"
age = 40
print("Name: %s, Age: %d" % (name, age))

---

13. Conclusion #

In this guide, we’ve covered the basic and advanced uses of the print() and input() functions in Python, which are essential for displaying output and gathering input from users. The flexibility of these functions allows you to handle text, numbers, and formatted output effectively, along with the ability to write and read from files.