def __init__(self, filename="db_test.csv"):
try:
self.db_file = open(filename, 'r+') # self.db_file is file variable for DB
except IOError:
FileProcessorExceptions.error_file_db_opening()#raising exception
self.db_filename = filename # name of DB file
self.last_line_num = 0 #number of last read line in database
def applyChanges(self, change_line_no, substitute_str=""):
""" Rewrites a database file if some record was deleted or modified """
old_name = self.db_filename
self.db_file.close()
if os.path.isfile(old_name + '.bak'): # rename data base file
os.remove(old_name + '.bak')
os.rename(old_name, old_name + '.bak')
self.db_file = open(old_name, mode='a') # creating new database file
bak_file = open(old_name+'.bak', mode='r')
lines_in_base_counter = 0
for line_counter, buffer in enumerate(bak_file): # copy records to new database file
if line_counter == change_line_no:
if substitute_str == "":
continue # deleting record
else:
buffer = ",".join(substitute_str) + "\n" # replaces the old record on a modified one
self.db_file.write(buffer) # appending line in new DB file
lines_in_base_counter += 1
bak_file.close() # close old DB file
self.db_file.close() # close new DB file
try:
self.db_file = open(self.db_filename, 'r+') # open new DB file
except IOError:
FileProcessorExceptions.error_file_db_opening()
return lines_in_base_counter # returns the number records in the database
def getLegend(self, filename="db_legend.csv"):
""" Reads legend and returns as list. """
with open(filename, 'r') as legend_file:
line = legend_file.readline()
if len(line) < 1: #if legend file is empty
FileProcessorExceptions.error_legend_reading() #raising exception
return Parser.Parser.parseString(line)
def getValuesFromCurrentLine(self):
""" Reads and returns the next record from the current line of the file. """
line = self.db_file.readline()
if len(line) < 1: #if database file is empty
FileProcessorExceptions.error_out_of_file() # raising exception
else:
self.last_line_num += 1
return Parser.Parser.parseString(string.rstrip(line))