Category: Python Answers

Sometimes, we want to detect whether a Python variable is a function.

In this article, we’ll look at how to detect whether a Python variable is a function.

How to detect whether a Python variable is a function?

To detect whether a Python variable is a function, we can call the callable function with the variable.

For instance, we write

is_func = callable(obj)

to call callable with obj to return True if obj is a function and False otherwise.

Conclusion

To detect whether a Python variable is a function, we can call the callable function with the variable.

Sometimes, we want to log while using multiprocessing in Python.

In this article, we’ll look at how to log while using multiprocessing in Python.

How to log while using multiprocessing in Python?

To log while using multiprocessing in Python, we can create a function to create a logger.

For instance, we write

def create_logger():
    import multiprocessing, logging
    logger = multiprocessing.get_logger()
    logger.setLevel(logging.INFO)
    formatter = logging.Formatter(\
        '[%(asctime)s| %(levelname)s| %(processName)s] %(message)s')
    handler = logging.FileHandler('logs/your_file_name.log')
    handler.setFormatter(formatter)

    if not len(logger.handlers): 
        logger.addHandler(handler)
    return logger

if __name__ == '__main__': 
    from multiprocessing import Pool
    logger = create_logger()
    logger.info('Starting pooling')
    p = Pool()

to create the create_logger function.

In it, we call multiprocessing.get_logger to create a logger object.

And then we get the handler for the logger with FileHandler to save log messages to logs/your_file_name.log.

Then we call setFormatter to use the formatter we get from Formatter.

Next, we call logger.addHandler with handler to use the FileHandler.

Next, we call create_logger to create the logger.

And then we call logger.info to log a message.

Conclusion

To log while using multiprocessing in Python, we can create a function to create a logger.

Sometimes, we want to convert JSON datetime between Python and JavaScript.

In this article, we’ll look at how to convert JSON datetime between Python and JavaScript.

How to convert JSON datetime between Python and JavaScript?

To convert JSON datetime between Python and JavaScript, we can use the strptime function to parse a JavaScript date string.

For instance, we write

from datetime import datetime

d = datetime.strptime('2022-01-08T19:00:00.123Z', '%Y-%m-%dT%H:%M:%S.%fZ')

to call strptime with the datetime string and a format string that matches the pattern for JavaScript datetime strings.

And then we call isoformat on the datetime to convert the datetime object back to a JavaScript date string with

s = d.isoformat() + 'Z'

We add 'Z' to specify that the time zone of the datetime is UTC.

Conclusion

To convert JSON datetime between Python and JavaScript, we can use the strptime function to parse a JavaScript date string.

Sometimes, we want to get a list from Pandas DataFrame column headers with Python.

In this article, we’ll look at how to get a list from Pandas DataFrame column headers with Python.

How to get a list from Pandas DataFrame column headers with Python?

To get a list from Pandas DataFrame column headers with Python, we can call list with the data frame object.

For instance, we write

columns = list(my_dataframe)

to call list with the my_dataframe data frame to return a list of column name strings in the data frame.

Conclusion

To get a list from Pandas DataFrame column headers with Python, we can call list with the data frame object.

Sometimes, we want to fix Python NameError: name is not defined.

In this article, we’ll look at how to fix Python NameError: name is not defined.

How to fix Python NameError: name is not defined?

To fix Python NameError: name is not defined, we can use a forward reference to annotate the type.

For instance, we write

class Tree:
    def __init__(self, left: 'Tree', right: 'Tree'):
        self.left = left
        self.right = right

to create the __init__ method with the left and right parameter set to the 'Tree' type.

This tells Python that left and right are Tree class instances without the class being defined yet.

Conclusion

To fix Python NameError: name is not defined, we can use a forward reference to annotate the type.