Python - Converting CSV to Objects - Code Design
- by victorhooi
Hi,
I have a small script we're using to read in a CSV file containing employees, and perform some basic manipulations on that data.
We read in the data (import_gd_dump), and create an Employees object, containing a list of Employee objects (maybe I should think of a better naming convention...lol). We then call clean_all_phone_numbers() on Employees, which calls clean_phone_number() on each Employee, as well as lookup_all_supervisors(), on Employees.
import csv
import re
import sys
#class CSVLoader:
# """Virtual class to assist with loading in CSV files."""
# def import_gd_dump(self, input_file='Gp Directory 20100331 original.csv'):
# gd_extract = csv.DictReader(open(input_file), dialect='excel')
# employees = []
# for row in gd_extract:
# curr_employee = Employee(row)
# employees.append(curr_employee)
# return employees
# #self.employees = {row['dbdirid']:row for row in gd_extract}
# Previously, this was inside a (virtual) class called "CSVLoader".
# However, according to here (http://tomayko.com/writings/the-static-method-thing) - the idiomatic way of doing this in Python is not with a class-fucntion but with a module-level function
def import_gd_dump(input_file='Gp Directory 20100331 original.csv'):
"""Return a list ('employee') of dict objects, taken from a Group Directory CSV file."""
gd_extract = csv.DictReader(open(input_file), dialect='excel')
employees = []
for row in gd_extract:
employees.append(row)
return employees
def write_gd_formatted(employees_dict, output_file="gd_formatted.csv"):
"""Read in an Employees() object, and write out each Employee() inside this to a CSV file"""
gd_output_fieldnames = ('hrid', 'mail', 'givenName', 'sn', 'dbcostcenter', 'dbdirid', 'hrreportsto', 'PHFull', 'PHFull_message', 'SupervisorEmail', 'SupervisorFirstName', 'SupervisorSurname')
try:
gd_formatted = csv.DictWriter(open(output_file, 'w', newline=''), fieldnames=gd_output_fieldnames, extrasaction='ignore', dialect='excel')
except IOError:
print('Unable to open file, IO error (Is it locked?)')
sys.exit(1)
headers = {n:n for n in gd_output_fieldnames}
gd_formatted.writerow(headers)
for employee in employees_dict.employee_list:
# We're using the employee object's inbuilt __dict__ attribute - hmm, is this good practice?
gd_formatted.writerow(employee.__dict__)
class Employee:
"""An Employee in the system, with employee attributes (name, email, cost-centre etc.)"""
def __init__(self, employee_attributes):
"""We use the Employee constructor to convert a dictionary into instance attributes."""
for k, v in employee_attributes.items():
setattr(self, k, v)
def clean_phone_number(self):
"""Perform some rudimentary checks and corrections, to make sure numbers are in the right format.
Numbers should be in the form 0XYYYYYYYY, where X is the area code, and Y is the local number."""
if self.telephoneNumber is None or self.telephoneNumber == '':
return '', 'Missing phone number.'
else:
standard_format = re.compile(r'^\+(?P<intl_prefix>\d{2})\((?P<area_code>\d)\)(?P<local_first_half>\d{4})-(?P<local_second_half>\d{4})')
extra_zero = re.compile(r'^\+(?P<intl_prefix>\d{2})\(0(?P<area_code>\d)\)(?P<local_first_half>\d{4})-(?P<local_second_half>\d{4})')
missing_hyphen = re.compile(r'^\+(?P<intl_prefix>\d{2})\(0(?P<area_code>\d)\)(?P<local_first_half>\d{4})(?P<local_second_half>\d{4})')
if standard_format.search(self.telephoneNumber):
result = standard_format.search(self.telephoneNumber)
return '0' + result.group('area_code') + result.group('local_first_half') + result.group('local_second_half'), ''
elif extra_zero.search(self.telephoneNumber):
result = extra_zero.search(self.telephoneNumber)
return '0' + result.group('area_code') + result.group('local_first_half') + result.group('local_second_half'), 'Extra zero in area code - ask user to remediate. '
elif missing_hyphen.search(self.telephoneNumber):
result = missing_hyphen.search(self.telephoneNumber)
return '0' + result.group('area_code') + result.group('local_first_half') + result.group('local_second_half'), 'Missing hyphen in local component - ask user to remediate. '
else:
return '', "Number didn't match recognised format. Original text is: " + self.telephoneNumber
class Employees:
def __init__(self, import_list):
self.employee_list = []
for employee in import_list:
self.employee_list.append(Employee(employee))
def clean_all_phone_numbers(self):
for employee in self.employee_list:
#Should we just set this directly in Employee.clean_phone_number() instead?
employee.PHFull, employee.PHFull_message = employee.clean_phone_number()
# Hmm, the search is O(n^2) - there's probably a better way of doing this search?
def lookup_all_supervisors(self):
for employee in self.employee_list:
if employee.hrreportsto is not None and employee.hrreportsto != '':
for supervisor in self.employee_list:
if supervisor.hrid == employee.hrreportsto:
(employee.SupervisorEmail, employee.SupervisorFirstName, employee.SupervisorSurname) = supervisor.mail, supervisor.givenName, supervisor.sn
break
else:
(employee.SupervisorEmail, employee.SupervisorFirstName, employee.SupervisorSurname) = ('Supervisor not found.', 'Supervisor not found.', 'Supervisor not found.')
else:
(employee.SupervisorEmail, employee.SupervisorFirstName, employee.SupervisorSurname) = ('Supervisor not set.', 'Supervisor not set.', 'Supervisor not set.')
#Is thre a more pythonic way of doing this?
def print_employees(self):
for employee in self.employee_list:
print(employee.__dict__)
if __name__ == '__main__':
db_employees = Employees(import_gd_dump())
db_employees.clean_all_phone_numbers()
db_employees.lookup_all_supervisors()
#db_employees.print_employees()
write_gd_formatted(db_employees)
Firstly, my preamble question is, can you see anything inherently wrong with the above, from either a class design or Python point-of-view? Is the logic/design sound?
Anyhow, to the specifics:
The Employees object has a method, clean_all_phone_numbers(), which calls clean_phone_number() on each Employee object inside it. Is this bad design? If so, why? Also, is the way I'm calling lookup_all_supervisors() bad?
Originally, I wrapped the clean_phone_number() and lookup_supervisor() method in a single function, with a single for-loop inside it. clean_phone_number is O(n), I believe, lookup_supervisor is O(n^2) - is it ok splitting it into two loops like this?
In clean_all_phone_numbers(), I'm looping on the Employee objects, and settings their values using return/assignment - should I be setting this inside clean_phone_number() itself?
There's also a few things that I'm sorted of hacked out, not sure if they're bad practice - e.g. print_employee() and gd_formatted() both use __dict__, and the constructor for Employee uses setattr() to convert a dictionary into instance attributes.
I'd value any thoughts at all. If you think the questions are too broad, let me know and I can repost as several split up (I just didn't want to pollute the boards with multiple similar questions, and the three questions are more or less fairly tightly related).
Cheers,
Victor
