Here is how to print to stderr in Python in Python.

import sys
print("This is an error message.", file=sys.stderr) 

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In Python, you can print to stderr by importing the sys module and using the sys.stderr.write() or print() method with the file parameter set to sys.stderr.

Alternatively you can also use:

import sys
sys.stderr.write("This is an error message.")

Extract extension from filename
Generate random integers between 0 and 9
Use a pythonic way to create a long multi-line string
Measure elapsed time in Python
Install specific package versions with pip
Read from stdin (standard input)
Get the class name of an instance
Check if a string is empty
Pad zeroes to a string
Delete an element from a dictionary
Check if a string is a float
Count the occurrences of an item in a list
Remove an element from a list by index
Use static methods
Remove a trailing newline
Print literal curly-brace characters in a string and also use .format on it
Exit/deactivate a virtualenv
Determine the type of an object
Limit floats to two decimal points
Know if an object has an attribute
Select an item from a list randomly
Read a file line-by-line into a list
Call a function of a module by using its name
Get the number of elements in a list
Print without a newline or space
Sort a list of dictionaries by a value of the dictionary
Remove a key from dictionary
Rename column names with Pandas
Lowercase a string
Upgrade all Python packages with pip
Get a substring of a string
Get the last element of a list
Parse a string to a float or integer
Convert a string into datetime format
Access environment variable values
Print coloured text on the terminal
Find current directory of a file
Change the size of figures drawn with Matplotlib
Manually raise an exception
Delete a file or folder
Split a list into evenly sized parts
Select rows from a DataFrame based on column values with Pandas
Install pip on Windows
Check if a given key already exists in a dictionary
Iterate over rows in a DataFrame for Pandas
Make function decorators and chain them together
Pass a variable by reference
Make a time delay
Convert bytes to a string
Copy a file
Concatenate two lists
Add new keys to a dictionary
Catch multiple exceptions in a single 'except' block
Check if a list is empty
Get the current time
Sort a dictionary by value
Use global variables in a function
List all files of a directory
Iterate over dictionaries using for loops
Check if a string contains a substring
Find the index of an item in a list
Understand how slice notation works
Make a flat list out of a list of lists
Accesses the index in for loops
Safely create a nested directory
Merge two dictionaries in a single expression
Check whether a file exists without exceptions
Convert a dictionary into a list
Convert a list into a dictionary
Duplicate a file
Append text in a text file
Use for loops
Deploy a web app to Heroku
Schedule a Python script for execution at a specific time every day
Store Python passwords securely on Windows, Mac, and Linux
Do dictionary comprehension
Do list comprehension
Create a virtual environment
Create a new file
Merge two lists
Extract items from two different lists into one list
Check if a text file is empty
Randomly select an item from a list
Generate a random integer
Break a while loop
Create a pandas DataFrame from a dictionary
Create a pandas DataFrame from a list
Get the last item of a list
Delete a column from a pandas dataframe
Access a column of a pandas dataframe
Create a class
Make a webpage request
Get the first two characters of a string
Loop through two lists at the same time