How to initialize python watchdog pattern matching event handler - python-3.x

Question

I'm using the Python Watchdog to monitor a directory for new files being created. Several different types of files are created in said directory but I only need to monitor a single file type, hence I use the Watchdog PatternMatchingEventHandler, where I specify the pattern to monitor using the patterns keyword.
To correctly execute the code under the hood (not displayed here) I need to initialize an empty dataframe in my event-handler, and I am having trouble getting this to work. If I remove the __init__ in the code below, everything works just fine btw.
I used the code in this answer as inspiration for my own.
The code I have set up looks as follows:
from watchdog.observers import Observer
from watchdog.events import PatternMatchingEventHandler
import time
import pandas as pd
import numpy as np
from multiprocessing import Pool
class HandlerEQ54(PatternMatchingEventHandler):
def __init__(self):
#Initializing an empty dataframe for storage purposes.
data_54 = pd.DataFrame(columns = ['Barcode','DUT','Step12','Step11','Np1','Np2','TimestampEQ54'])
#Converting to INT for later purposes
data_54[['Barcode','DUT']]=data_54[['Barcode','DUT']].astype(np.int64)
self.data = data_54
def on_created(self,event):
if event.is_directory:
return True
elif event.event_type == 'created':
#Take action here when a file is created.
print('Found new files:')
print(event.src_path)
time.sleep(0.1)
#Creating process pool to return data
pool1 = Pool(processes=4)
#Pass file to parsing function and return parsed result.
result_54 = pool1.starmap(parse_eq54,[(event.src_path,self.data)])
#returns the dataframe rather than the list of dataframes returned by starmap
self.data = result_54[0]
print('Data read: ')
print(self.data)
def monitorEquipment(equipment):
'''Uses the Watchdog package to monitor the data directory for new files.
See the HandlerEQ54 and HandlerEQ51 classes in multiprocessing_handlers for actual monitoring code. Monitors each equipment.'''
print('equipment')
if equipment.upper() == 'EQ54':
event_handler = HandlerEQ54(patterns=["*.log"])
filepath = '/path/to/first/file/source/'
# set up observer
observer = Observer()
observer.schedule(event_handler, path=filepath, recursive=True)
observer.daemon=True
observer.start()
print('Observer started')
# monitor
try:
while True:
time.sleep(5)
except KeyboardInterrupt:
observer.unschedule_all()
observer.stop()
observer.join()
However, when I execute monitorEquipment I receive the following error message:
TypeError: __init__() got an unexpected keyword argument 'patterns'
Evidently I'm doing something wrong when I'm initializing my handler class, but I'm drawing a blank as to what that is (which probably reflects my less-than-optimal understanding of classes). Can someone advice me on how to correctly initialize the empty dataframe in my HandlerEQ54 class, to not get the error I do?

Answer 1

Looks like you are missing the patterns argument from your __init__ method, you'll also need a super() call to the __init__ method of the parent class (PatternMatchingEventHandler), so you can pass the patterns argument upwards.
it should look something like this:
class HandlerEQ54(PatternMatchingEventHandler):
def __init__(self, patterns=None):
super(HandlerEQ54, self).__init__(patterns=patterns)
...
event_handler = HandlerEQ54(patterns=["*.log"])
or, for a more generic case and to support all of PatternMatchingEventHandler's arguments:
class HandlerEQ54(PatternMatchingEventHandler):
def __init__(self, *args, **kwargs):
super(HandlerEQ54, self).__init__(*args, **kwargs)
...
event_handler = HandlerEQ54(patterns=["*.log"])