watchdog(python) - monitor only one file format and ignore everything else in 'PatternMatchingEventHandler'

问题

I'm running code from this article and made some changes to monitor file creations/additions of only one format, that's .csv in a specified directory.

the problem now is:

My program breaks(stops monitoring, but keeps running), whenever the new file added is not of .csv format; and to compensate for that, here's what i did with ignore_patterns argument(but the program still stops monitoring after a new file of other format is added):
PatternMatchingEventHandler(patterns="*.csv", ignore_patterns=["*~"], ignore_directories=True, case_sensitive=True)

the complete code is:

import time
import csv
from datetime import datetime
from watchdog.observers import Observer
from watchdog.events import PatternMatchingEventHandler
from os import path
from pandas import read_csv
# class that takes care of everything
class file_validator(PatternMatchingEventHandler):
    def __init__(self, source_path):
        # setting parameters for 'PatternMatchingEventHandler'
        super(file_validator, self).__init__(patterns="*.csv", ignore_patterns=["*~"], ignore_directories=True, case_sensitive=True)
        self.source_path = source_path
        self.print_info = None

    def on_created(self, event):
        # this is the new file that was created
        new_file = event.src_path
        # details of each new .csv file
        # demographic details
        file_name = path.basename(new_file)
        file_size = f"{path.getsize(new_file) / 1000} KiB"
        file_creation = f"{datetime.fromtimestamp(path.getmtime(new_file)).strftime('%Y-%m-%d %H:%M:%S')}"
        new_data = read_csv(new_file)
        # more details
        number_columns = new_data.shape[1]
        data_types_data = [
            ('float' if i == 'float64' else ('int' if i == 'int64' else ('character' if i == 'object' else i))) for i in
            [x.name for x in list(new_data.dtypes)]]
        null_count_data = list(dict(new_data.isna().sum()).values())
        print(f"{file_name}, {file_size}, {file_creation}, {number_columns}")
        # trying to access this info, but of no help
        self.print_info = f"{file_name}, {file_size}, {file_creation}, {number_columns}"

    def return_logs(self):
        return self.print_info

# main function    
if __name__ == "__main__":
    some_path = "C:\\Users\\neevaN_Reddy\\Documents\\learning dash\\"
    my_validator = file_validator(source_path=some_path)
    my_observer = Observer()
    my_observer.schedule(my_validator, some_path, recursive=True)
    my_observer.start()
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        my_observer.stop()
        my_observer.join()
    # # this doesn't print anything
    print(my_validator.return_logs)

EDIT 1(after Quentin Pradet's comment): after your suggestion in the comment I've changed my arguments to:

super(file_validator, self).__init__(patterns="*.csv",
                                     # ignore_patterns=["*~"],
                                     ignore_directories=True, 
                                     case_sensitive=True)

and when I copy files of other format(i tried with .ipynb file), this error is what i see(also program stops monitoring even .csv files after this):

Exception in thread Thread-1:
Traceback (most recent call last):
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\threading.py", line 926, in _bootstrap_inner
    self.run()
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\api.py", line 199, in run
    self.dispatch_events(self.event_queue, self.timeout)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\observers\api.py", line 368, in dispatch_events
    handler.dispatch(event)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\watchdog\events.py", line 454, in dispatch
    _method_map[event_type](event)
  File "C:/Users/neevaN_Reddy/Documents/Work/Project-Aretaeus/diabetes_risk project/file validation using a class.py", line 26, in on_created
    new_data = read_csv(new_file)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parsers.py", line 685, in parser_f
    return _read(filepath_or_buffer, kwds)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parsers.py", line 463, in _read
    data = parser.read(nrows)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parsers.py", line 1154, in read
    ret = self._engine.read(nrows)
  File "C:\Users\neevaN_Reddy\AppData\Local\Programs\Python\Python37\lib\site-packages\pandas\io\parsers.py", line 2059, in read
    data = self._reader.read(nrows)
  File "pandas/_libs/parsers.pyx", line 881, in pandas._libs.parsers.TextReader.read
  File "pandas/_libs/parsers.pyx", line 896, in pandas._libs.parsers.TextReader._read_low_memory
  File "pandas/_libs/parsers.pyx", line 950, in pandas._libs.parsers.TextReader._read_rows
  File "pandas/_libs/parsers.pyx", line 937, in pandas._libs.parsers.TextReader._tokenize_rows
  File "pandas/_libs/parsers.pyx", line 2132, in pandas._libs.parsers.raise_parser_error
pandas.errors.ParserError: Error tokenizing data. C error: Expected 1 fields in line 4, saw 2

apparently, there is some error with pandas, which means my on_created function is being triggered for file formats that are not .csv too, which i presume mean that something has to go in ignore_patterns argument to not have the on_created function triggered when a file of some other format is added.

回答1:

Can you try sending patterns as a list instead of a string, eg. patterns=["*.csv"]?

来源：https://stackoverflow.com/questions/59063532/watchdogpython-monitor-only-one-file-format-and-ignore-everything-else-in-p