search in each of the s3 bucket and see if the given folder exists

This is maybe a lengthy process.

 buckets = ['PDF','TXT','PNG','JPG']
    s3_client = getclient('s3')
    for i in buckets:
        result = s3_client.list_objects(Bucket= i, Prefix='', Delimiter ='')
        contents = result.get('Contents')
        for content in contents:
            if 'processed/files/' in content.get('Key'):
                print("Do the process")

You can get the list of directories from the s3 bucket. If it contains the required folder do the required process.

import boto3

client = boto3.client('s3')
bucket_name = "bucket_name"
prefix = ""

s3 = boto3.client("s3")

result = client.list_objects(Bucket=bucket_name, Delimiter='/')
   for obj in result.get('CommonPrefixes'):  
       prefix = obj.get('Prefix')
       file_list = ListFiles(client,bucket_name,prefix)
       for file in file_list:
          if "processed/files" in file:

def ListFiles(client, bucket_name, prefix):
    _BUCKET_NAME = bucket_name
    _PREFIX = prefix
    """List files in specific S3 URL"""
    response = client.list_objects(Bucket=_BUCKET_NAME, Prefix=_PREFIX)

    for content in response.get('Contents', []):
        yield content.get('Key')

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