1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
import csv
from ywalk.types import Connection, Mode, Place
FIELD_NAMES = ['Origin', 'Destination', 'Mode', 'Time']
class InputError(Exception):
def __init__(self, message, file, line, context):
super().__init__(message)
self.message = message
self.file = file
self.line = line
self.context = context
def __str__(self):
return f'{self.file}:{self.line}: {self.message}\n {self.context}'
def parse_row(row):
for field in FIELD_NAMES:
if row[field] is None:
raise ValueError(f'Empty field \'{field}\'')
# This is an enum lookup, not a creation. The Enum class replaces a custom
# __new__ after class creation with one that only does lookups.
# pylint: disable=no-value-for-parameter
mode = Mode(row['Mode'])
time = int(row['Time'])
if time < 0:
raise ValueError('Negative travel time')
return Connection(Place(row['Origin']), Place(row['Destination']), mode, time)
def check_fieldnames(names):
for name in FIELD_NAMES:
if name not in names:
raise ValueError(f'Missing field \'{name}\' in {names}')
def parse_tsv(path):
with open(path, encoding='utf-8', newline='') as file:
reader = csv.DictReader(file, dialect=csv.excel_tab)
check_fieldnames(reader.fieldnames)
for line, row in enumerate(reader):
try:
yield parse_row(row)
except ValueError as err:
raise InputError(err, path, line + 1, row) from err
|