Python Print to Stderr

3 ways to print to stderr in Python:

  1. Using stderr
  2. Using sys.stderr.write()
  3. Using logging module

Method 1 : Using stderr

The sys.stderr stream is typically used for outputting error messages.

You can use the file argument of the print function to direct the output to stderr.

Visual Representation

Visual Representation of Python Print to Stderr

Example

import sys

# Print an error message to stderr
print("That's an error", file=sys.stderr)

Output

That's an error

Method 2: Using sys.stderr.write()

The write() method is useful when you need more control over the formatting of the error messages.

Unlike print(), which automatically adds a newline at the end of the output, write() does not add a newline. So, you need to include it manually if required.

Visual Representation

Visual Representation of Using sys.stderr.write()

Example

import sys

sys.stderr.write("That's an error\n") 

Output

That's an error

Method 3: Using logging module

The logging module is widely used for both development and production environments and offers various levels of severity for log messages, such as DEBUG, INFO, WARNING(default), ERROR, and CRITICAL.

Visual Representation

Visual Representation of Using logging module

Example

import logging

# Configure logging to handle error level messages
logging.basicConfig(level=logging.ERROR)

# Log an error message
logging.error("That's an error")

Output

That's an error

That’s it.

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