Category: Python Answers

Sometimes, we want to grow a list without getting IndexError: list assignment index out of range with Python.

In this article, we’ll look at how to grow a list without getting IndexError: list assignment index out of range with Python.

How to grow a list without getting IndexError: list assignment index out of range with Python?

To grow a list without getting IndexError: list assignment index out of range with Python, we can use the append method.

For instance, we write

for l in i:
    j.append(l)

to call j.append with l to append the element l to list j.

Conclusion

To grow a list without getting IndexError: list assignment index out of range with Python, we can use the append method.

Sometimes, we want to fix TypeError: ‘str’ does not support the buffer interface with Python.

In this article, we’ll look at how to fix TypeError: ‘str’ does not support the buffer interface with Python.

How to fix TypeError: ‘str’ does not support the buffer interface with Python?

To fix TypeError: ‘str’ does not support the buffer interface with Python, we should call a file’s write method with bytes if the file is opened as a binary file.

For instance, we write

plaintext = input("Please enter the text you want to compress")
filename = input("Please enter the desired filename")

with gzip.open(filename + ".gz", "wb") as outfile:
    outfile.write(bytes(plaintext, 'UTF-8'))

to call open the file with gzip.open as a writable binary file with 'wb'.

Then we call outfile.write with plaintext converted to bytes with bytes before writing it to the opened file.

Conclusion

To fix TypeError: ‘str’ does not support the buffer interface with Python, we should call a file’s write method with bytes if the file is opened as a binary file.

Sometimes, we want to time out function if it takes too long to finish with Python.

In this article, we’ll look at how to time out function if it takes too long to finish with Python.

How to time out function if it takes too long to finish with Python?

To time out function if it takes too long to finish with Python, we can use the signal module.

For instance, we write

import signal

class timeout:
    def __init__(self, seconds=1, error_message='Timeout'):
        self.seconds = seconds
        self.error_message = error_message

    def handle_timeout(self, signum, frame):
        raise TimeoutError(self.error_message)

    def __enter__(self):
        signal.signal(signal.SIGALRM, self.handle_timeout)
        signal.alarm(self.seconds)

    def __exit__(self, type, value, traceback):
        signal.alarm(0)

with timeout(seconds=3):
    time.sleep(4)

to create the timeout class.

It has the handle_timeout method that raises a TimeoutError.

And it has the __enter__ method that calls signal.signal to listen for the the signal.SIGALRM signal and calls handle_timeout if it’s emitted.

And then we call signal.alarm with the timeout value to emit the signal.SIGALRM signal after seconds has elapsed.

In __exit__ we call signal_alarm with with 0 to reset the alarm.

Then we call timeout with the seconds argument to raise a TimeoutError if the code in the with block has timed out.

Conclusion

To time out function if it takes too long to finish with Python, we can use the signal module.

Sometimes, we want to check file size in Python

In this article, we’ll look at how to check file size in Python.

How to check file size in Python?

To check file size in Python, we can use the st_size property.

For instance, we write

from pathlib import Path

size = Path("somefile.txt").stat().st_size

to get the stats for the file with

Path("somefile.txt").stat()

Then we get the size of somefile.txt with the st_size property in bytes.

Conclusion

To check file size in Python, we can use the st_size property.

Sometimes, we want to iterate through a range of dates in Python.

In this article, we’ll look at how to iterate through a range of dates in Python.

How to iterate through a range of dates in Python?

To iterate through a range of dates in Python, we can use a while loop.,

For instance, we write

from datetime import date, timedelta

start_date = date(2020, 1, 1)
end_date = date(2021, 1, 1)
delta = timedelta(days=1)

while start_date <= end_date:
    print(start_date.strftime("%Y-%m-%d"))
    start_date += delta

to add a while loop that loops from the initial value of start_date to end_date by using the start_date <= end_date condition for the while loop.

In the loop body, we print the current start_date and then add timedelta to start_date at the end of each iterator.

Conclusion

To iterate through a range of dates in Python, we can use a while loop.,