Read from File, or STDIN in python

Read from File, or STDIN in python

In Python, you can read input from both files and standard input (STDIN). You can use the input() function for reading from STDIN, and you can use various methods to read from a file. Here's how to do both:

Reading from STDIN (Standard Input):

To read input from STDIN, you can use the input() function. It reads a line of text from the standard input and returns it as a string.

user_input = input("Enter something: ") print("You entered:", user_input)

When you run this code, it will prompt you to enter something, and it will then display what you entered.

Reading from a File:

To read from a file, you can use the open() function to open the file, and then you can use various methods like read(), readline(), or readlines() to read the file's contents. Here's an example using readlines() to read lines from a file:

# Open the file in read mode with open('example.txt', 'r') as file: lines = file.readlines() # Iterate through the lines and print them for line in lines: print(line.strip()) # .strip() removes leading/trailing whitespace and newlines

In this code:

  1. We open the file 'example.txt' in read mode using a with statement to ensure that the file is properly closed when done.

  2. We use file.readlines() to read all lines from the file into a list.

  3. We iterate through the lines and print them, using strip() to remove leading/trailing whitespace and newlines.

You can replace 'example.txt' with the path to the file you want to read. Depending on your needs, you may choose different methods (read(), readline(), or others) to read file contents.

Examples

  1. Read from File or STDIN in Python

    • This snippet demonstrates how to read from a file if a filename is provided, or from STDIN if not.
    import sys file_path = "example.txt" # Replace with None or "" for STDIN if file_path: with open(file_path, "r") as f: content = f.read() else: content = sys.stdin.read() # Read from STDIN print(content)

  2. Read Lines from File or STDIN in Python

    • This code snippet shows how to read lines from a file or STDIN.
    import sys file_path = "example.txt" # Replace with None for STDIN if file_path: with open(file_path, "r") as f: lines = f.readlines() else: lines = sys.stdin.readlines() for line in lines: print(line.strip()) # Processing each line

  3. Read File Path from Command Line or Use STDIN

    • This snippet demonstrates how to read a file path from command-line arguments or use STDIN if no arguments are provided.
    import sys # Check if there's a command-line argument for the file path file_path = sys.argv[1] if len(sys.argv) > 1 else None if file_path: with open(file_path, "r") as f: content = f.read() else: content = sys.stdin.read() print(content)

  4. Reading CSV from File or STDIN in Python

    • This snippet shows how to read CSV data from a file or STDIN.
    import sys import csv file_path = "example.csv" # Replace with None for STDIN if file_path: with open(file_path, "r") as f: reader = csv.reader(f) data = list(reader) # Read CSV data into a list else: reader = csv.reader(sys.stdin) data = list(reader) for row in data: print(row)

  5. Reading from File or STDIN with Default Data

    • This snippet demonstrates how to read from a file or STDIN with a fallback default if STDIN is empty.
    import sys file_path = None # Set to None to read from STDIN default_data = "Default content" # Default data if STDIN is empty if file_path: with open(file_path, "r") as f: content = f.read() else: content = sys.stdin.read().strip() or default_data # Use default if STDIN is empty print(content)

  6. Reading Binary Data from File or STDIN in Python

    • This snippet demonstrates how to read binary data from a file or STDIN.
    import sys file_path = None # Read from STDIN by default if file_path: with open(file_path, "rb") as f: binary_data = f.read() else: binary_data = sys.stdin.buffer.read() # Read binary from STDIN print(binary_data)

  7. Processing File or STDIN Data with Regex

    • This snippet shows how to read from a file or STDIN and process its content using regular expressions.
    import sys import re file_path = "example.txt" # Replace with None for STDIN if file_path: with open(file_path, "r") as f: content = f.read() else: content = sys.stdin.read() words = re.findall(r"\w+", content) # Extract words using regex print(words)

  8. Count Lines from File or STDIN in Python

    • This snippet demonstrates how to count lines from a file or STDIN.
    import sys file_path = "example.txt" # Set to None for STDIN if file_path: with open(file_path, "r") as f: line_count = len(f.readlines()) else: line_count = len(sys.stdin.readlines()) print("Number of lines:", line_count)

  9. Read from File or STDIN with Context

    • This snippet shows how to read from a file or STDIN and use a context (such as an environment variable or default value) for additional configuration.
    import sys import os file_path = os.getenv("FILE_PATH", None) # Retrieve from environment variable default_text = "Default content" # Default if STDIN is empty if file_path: with open(file_path, "r") as f: content = f.read() else: content = sys.stdin.read().strip() or default_text # Use default if empty print(content)

  10. Reading from File or STDIN with Command Line Options

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