Python Input and Output

In this Python Input and Output tutorial, we'll cover the basics of reading and writing data in Python. We'll focus on the following topics:

Basic Output: Print
Basic Input: Input
File I/O: Reading and Writing Files

1. Basic Output: Print

The print() function in Python is used to output data to the console. By default, it prints the data followed by a newline character.

Syntax:

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

Example:

print("Hello, World!")

Output:

Hello, World!

2. Basic Input: Input

The input() function in Python is used to read a line of text from the user (input from the console). It returns the input as a string.

Syntax:

input(prompt)

Example:

name = input("What's your name? ")
print(f"Hello, {name}!")

Output:

What's your name? John
Hello, John!

3. File I/O: Reading and Writing Files

To work with files, we need to open them using the open() function, which returns a file object. The most common modes are:

'r': Read (default)
'w': Write (truncate the file first)
'a': Append
'x': Create (if the file doesn't exist)

Reading from a file

with open('file.txt', 'r') as file:
    content = file.read()
print(content)

Writing to a file

with open('file.txt', 'w') as file:
    file.write('Hello, World!')

Appending to a file

with open('file.txt', 'a') as file:
    file.write('\nThis line is appended to the file.')

Reading and writing line by line

Reading:

with open('file.txt', 'r') as file:
    for line in file:
        print(line.strip())

Writing:

lines = ['Line 1', 'Line 2', 'Line 3']

with open('file.txt', 'w') as file:
    for line in lines:
        file.write(f'{line}\n')

That's it! You now have a basic understanding of how to handle input and output operations in Python. Keep practicing and exploring more advanced features to improve your skills.

How to take user input in Python:
- Description: To take user input in Python, use the input() function. It reads a line from the user and returns it as a string.
- Code:
```
user_input = input("Enter something: ")
print("You entered:", user_input)
```
Reading and writing files in Python:
- Description: Python provides functions for reading (open() with mode 'r') and writing (open() with mode 'w') files.
- Code (Reading):
```
with open("example.txt", "r") as file:
    content = file.read()
    print(content)
```
- Code (Writing):
```
with open("example.txt", "w") as file:
    file.write("Hello, File!")
```
Formatted output in Python:
- Description: Use formatted strings (f-strings) or the format() method for formatted output in Python.
- Code (f-strings):
```
name = "Alice"
age = 25
print(f"Name: {name}, Age: {age}")
```
- Code (format() method):
```
name = "Bob"
age = 30
print("Name: {}, Age: {}".format(name, age))
```
Using input() function in Python:
- Description: The input() function is used to get user input in Python. It returns a string, and you can convert it to the desired data type if needed.
- Code:
```
age_str = input("Enter your age: ")
age = int(age_str)
print(f"Your age is: {age}")
```
File handling in Python for input and output:
- Description: File handling involves operations like opening, reading, writing, and closing files using the open() function.
- Code (Read and Write):
```
with open("example.txt", "r") as file:
    content = file.read()
    print(content)

with open("output.txt", "w") as file:
    file.write("Writing to a file!")
```
Standard input and output in Python:
- Description: Standard input (stdin) and output (stdout) are commonly used for reading from the keyboard and printing to the console.
- Code:
```
user_input = input("Enter something: ")
print("You entered:", user_input)
```
Reading and writing to text files in Python:
- Description: Reading and writing to text files involves using the open() function with appropriate modes ('r' for reading, 'w' for writing).
- Code (Read and Write):
```
with open("example.txt", "r") as file:
    content = file.read()
    print(content)

with open("output.txt", "w") as file:
    file.write("Writing to a text file!")
```
Python input validation and error handling:
- Description: Input validation involves checking user input for correctness. Error handling with try-except blocks helps manage unexpected situations.
- Code (Input Validation):
```
while True:
    try:
        age = int(input("Enter your age: "))
        break
    except ValueError:
        print("Invalid input. Please enter a valid number.")
print(f"Your age is: {age}")
```