Creating csv for Gsuite bulk upload and Mailchimp bulk notifications

Gsuite.py

from random import randint
import openpyxl

parent_str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

ob = openpyxl.load_workbook("College Mail Id for ECE (Responses).xlsx")
sh = ob["Form Responses 1"]

pwd_log = []
def create_password():
	'''
	Creates password for user
	'''
	pwd = ''
	for _ in range(12):
		pwd+=parent_str[randint(0,60)]
	pwd_log.append(pwd+'\n')
	return pwd


def split_name(row=2,column=1):
	'''
	Separates first and last name of user i
	'''
	name = str(sh.cell(row=row,column=column).value).upper().strip().split(' ')
	first_name = name[0]
	last_name = ' '.join(name[1:])
	return (first_name,last_name)


def get_primary_mail(row=2,column=1,pass_year='20',batch='ece'):
	'''
	Creates primary mail address for user i
	'''

	first_name,last_name = split_name(row,column)
	roll = str(sh.cell(row=row,column=2).value)[-2:]
	new_mail_id = first_name[0].lower()*int(first_name[0]!=' ')+last_name[0].lower()*int(last_name[0]!=' ')+pass_year+roll+'@'+batch+'.jgec.ac.in'
	return new_mail_id

def get_secondary_mail(row=2,column=3):
	'''
	Returns mail address for user i
	'''
	return str(sh.cell(row=row,column=column).value)


def return_output():
	'''
	Returns list of strings to be written in users.csv
	'''
	write,string = [],''

	for user in range(2,sh.max_row+1):
		first_name,last_name=split_name(user,1)
		string+=first_name+','
		string+=last_name+','
		string+=get_primary_mail(user,1,'20','ece')+','
		string+=create_password()+',,'
		string+='/Students/ECE/2020 batch,'
		string+=get_secondary_mail(user,3)+',,,,,,,,,,,,,,,,,'+'True\n'
		write.append(string)
		string=''

	return write

def main():
	'''
	Writes to users.csv
	'''

	output = return_output()


	with open("users.csv","a+") as f:
		f.writelines(output)
		
	with open("pwd.log","w+") as f:
		f.writelines(pwd_log)
		
	f_in = open("users.csv","r+")
	f = open("mailchimp.csv","w+")
	string=''
	f.write('Email address,FNAME,LNAME,JGECMAIL,PWD\n')
	for line in f_in:
		string = line[line.find('batch')+6:line.find(',,,,,,,')]+','
		string += line[:line.find(',,')]
		f.write(string+'\n')
	f.close()	

if __name__ == '__main__':
	main()