pylint/pep8 fixes

21 files changed, 141 insertions, 52 deletions

diff --git a/bin/mutual_friends.py b/bin/mutual_friends.py
index 82015bb..550d957 100644
--- a/bin/mutual_friends.py
+++ b/bin/mutual_friends.py
@@ -14,22 +14,27 @@ from vk.user import UserField
 
 from .utils import io
 
+
 _OUTPUT_USER_FIELDS = UserField.UID, UserField.FIRST_NAME, UserField.LAST_NAME
 
+
 def _query_friend_list(api, user):
     return api.friends_get(user.get_uid(), fields=_OUTPUT_USER_FIELDS)
 
+
 def _filter_user_fields(user):
     new_user = OrderedDict()
     for field in _OUTPUT_USER_FIELDS:
         new_user[str(field)] = user[field] if field in user else None
     return new_user
 
+
 class OutputSinkMutualFriends(metaclass=abc.ABCMeta):
     @abc.abstractmethod
     def write_mutual_friends(self, friend_list):
         pass
 
+
 class OutputSinkCSV(OutputSinkMutualFriends):
     def __init__(self, fd=sys.stdout):
         self._writer = io.FileWriterCSV(fd)
@@ -38,6 +43,7 @@ class OutputSinkCSV(OutputSinkMutualFriends):
         for user in friend_list:
             self._writer.write_row(user.values())
 
+
 class OutputSinkJSON(OutputSinkMutualFriends):
     def __init__(self, fd=sys.stdout):
         self._writer = io.FileWriterJSON(fd)
@@ -45,6 +51,7 @@ class OutputSinkJSON(OutputSinkMutualFriends):
     def write_mutual_friends(self, friend_list):
         self._writer.write(friend_list)
 
+
 class OutputFormat(Enum):
     CSV = 'csv'
     JSON = 'json'
@@ -59,10 +66,10 @@ class OutputFormat(Enum):
     def create_sink(self, fd=sys.stdout):
         if self is OutputFormat.CSV:
             return OutputSinkCSV(fd)
-        elif self is OutputFormat.JSON:
+        if self is OutputFormat.JSON:
             return OutputSinkJSON(fd)
-        else:
-            raise NotImplementedError('unsupported output format: ' + str(self))
+        raise NotImplementedError('unsupported output format: ' + str(self))
+
 
 def _parse_output_format(s):
     try:
@@ -70,6 +77,7 @@ def _parse_output_format(s):
     except ValueError:
         raise argparse.ArgumentTypeError('invalid output format: ' + s)
 
+
 def _parse_args(args=None):
     if args is None:
         args = sys.argv[1:]
@@ -89,6 +97,7 @@ def _parse_args(args=None):
 
     return parser.parse_args(args)
 
+
 def write_mutual_friends(uids, out_path=None, out_fmt=OutputFormat.CSV):
     api = API()
     users = api.users_get(uids)
@@ -101,8 +110,10 @@ def write_mutual_friends(uids, out_path=None, out_fmt=OutputFormat.CSV):
         sink = out_fmt.create_sink(out_fd)
         sink.write_mutual_friends(mutual_friends)
 
+
 def main(args=None):
     write_mutual_friends(**vars(_parse_args(args)))
 
+
 if __name__ == '__main__':
     main()
diff --git a/bin/online_sessions.py b/bin/online_sessions.py
index 670a8c3..e0de7c9 100644
--- a/bin/online_sessions.py
+++ b/bin/online_sessions.py
@@ -17,6 +17,7 @@ from vk.user import UserField
 from .utils.bar_chart import BarChartBuilder
 from .utils import io
 
+
 class GroupBy(Enum):
     USER = 'user'
     DATE = 'date'
@@ -30,14 +31,14 @@ class GroupBy(Enum):
         online_streaks = OnlineSessionEnumerator(time_from, time_to)
         if self is GroupBy.USER:
             return online_streaks.group_by_user(db_reader)
-        elif self is GroupBy.DATE:
+        if self is GroupBy.DATE:
             return online_streaks.group_by_date(db_reader)
-        elif self is GroupBy.WEEKDAY:
+        if self is GroupBy.WEEKDAY:
             return online_streaks.group_by_weekday(db_reader)
-        elif self is GroupBy.HOUR:
+        if self is GroupBy.HOUR:
             return online_streaks.group_by_hour(db_reader)
-        else:
-            raise NotImplementedError('unsupported grouping: ' + str(self))
+        raise NotImplementedError('unsupported grouping: ' + str(self))
+
 
 _OUTPUT_USER_FIELDS = (
     UserField.UID,
@@ -46,11 +47,13 @@ _OUTPUT_USER_FIELDS = (
     UserField.DOMAIN,
 )
 
+
 class OutputSinkOnlineSessions(metaclass=abc.ABCMeta):
     @abc.abstractmethod
     def process_database(self, group_by, db_reader, time_from=None, time_to=None):
         pass
 
+
 class OutputConverterCSV:
     @staticmethod
     def convert_user(user):
@@ -68,6 +71,7 @@ class OutputConverterCSV:
     def convert_hour(hour):
         return [str(timedelta(hours=hour))]
 
+
 class OutputSinkCSV(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
         self._writer = io.FileWriterCSV(fd)
@@ -91,6 +95,7 @@ class OutputSinkCSV(OutputSinkOnlineSessions):
             row.append(str(duration))
             self._writer.write_row(row)
 
+
 class OutputConverterJSON:
     _DATE_FIELD = 'date'
     _WEEKDAY_FIELD = 'weekday'
@@ -125,6 +130,7 @@ class OutputConverterJSON:
         obj[OutputConverterJSON._HOUR_FIELD] = str(timedelta(hours=hour))
         return obj
 
+
 class OutputSinkJSON(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
         self._writer = io.FileWriterJSON(fd)
@@ -142,7 +148,7 @@ class OutputSinkJSON(OutputSinkOnlineSessions):
 
     @staticmethod
     def _key_to_object(group_by, key):
-        if not group_by in OutputSinkJSON._CONVERT_KEY:
+        if group_by not in OutputSinkJSON._CONVERT_KEY:
             raise NotImplementedError('unsupported grouping: ' + str(group_by))
         return OutputSinkJSON._CONVERT_KEY[group_by](key)
 
@@ -154,6 +160,7 @@ class OutputSinkJSON(OutputSinkOnlineSessions):
             entries.append(entry)
         self._writer.write(entries)
 
+
 class OutputConverterPlot:
     @staticmethod
     def convert_user(user):
@@ -171,6 +178,7 @@ class OutputConverterPlot:
     def convert_hour(hour):
         return '{}:00'.format(hour)
 
+
 class OutputSinkPlot(OutputSinkOnlineSessions):
     def __init__(self, fd=sys.stdout):
         self._fd = fd
@@ -200,11 +208,11 @@ class OutputSinkPlot(OutputSinkOnlineSessions):
 
     @staticmethod
     def _extract_labels(group_by, durations):
-        return tuple(map(lambda key: OutputSinkPlot._format_key(group_by, key), durations.keys()))
+        return (OutputSinkPlot._format_key(group_by, key) for key in durations.keys())
 
     @staticmethod
     def _extract_values(durations):
-        return tuple(map(OutputSinkPlot._duration_to_seconds, durations.values()))
+        return (OutputSinkPlot._duration_to_seconds(duration) for duration in durations.values())
 
     def process_database(
             self, group_by, db_reader, time_from=None, time_to=None):
@@ -219,8 +227,8 @@ class OutputSinkPlot(OutputSinkOnlineSessions):
                                fontsize='small', rotation=30)
         bar_chart.set_value_label_formatter(self._format_duration)
 
-        labels = self._extract_labels(group_by, durations)
-        durations = self._extract_values(durations)
+        labels = tuple(self._extract_labels(group_by, durations))
+        durations = tuple(self._extract_values(durations))
 
         if group_by is GroupBy.HOUR:
             bar_chart.labels_align_middle = False
@@ -237,6 +245,7 @@ class OutputSinkPlot(OutputSinkOnlineSessions):
         else:
             bar_chart.save(self._fd)
 
+
 class OutputFormat(Enum):
     CSV = 'csv'
     JSON = 'json'
@@ -248,38 +257,42 @@ class OutputFormat(Enum):
     def create_sink(self, fd=sys.stdout):
         if self is OutputFormat.CSV:
             return OutputSinkCSV(fd)
-        elif self is OutputFormat.JSON:
+        if self is OutputFormat.JSON:
             return OutputSinkJSON(fd)
-        elif self is OutputFormat.PLOT:
+        if self is OutputFormat.PLOT:
             return OutputSinkPlot(fd)
-        else:
-            raise NotImplementedError('unsupported output format: ' + str(self))
+        raise NotImplementedError('unsupported output format: ' + str(self))
 
     def open_file(self, path=None):
         if self is OutputFormat.PLOT:
             return io.open_output_binary_file(path)
         return io.open_output_text_file(path)
 
+
 def _parse_group_by(s):
     try:
         return GroupBy(s)
     except ValueError:
         raise argparse.ArgumentTypeError('invalid "group by" value: ' + s)
 
+
 def _parse_database_format(s):
     try:
         return DatabaseFormat(s)
     except ValueError:
         raise argparse.ArgumentTypeError('invalid database format: ' + s)
 
+
 def _parse_output_format(s):
     try:
         return OutputFormat(s)
     except ValueError:
         raise argparse.ArgumentTypeError('invalid output format: ' + s)
 
+
 _DATE_RANGE_LIMIT_FORMAT = '%Y-%m-%dT%H:%M:%SZ'
 
+
 def _parse_date_range_limit(s):
     try:
         dt = datetime.strptime(s, _DATE_RANGE_LIMIT_FORMAT)
@@ -289,6 +302,7 @@ def _parse_date_range_limit(s):
         raise argparse.ArgumentTypeError(
             msg.format(_DATE_RANGE_LIMIT_FORMAT, s))
 
+
 def _parse_args(args=None):
     if args is None:
         args = sys.argv[1:]
@@ -324,6 +338,7 @@ def _parse_args(args=None):
 
     return parser.parse_args(args)
 
+
 def process_online_sessions(
         db_path=None, db_fmt=DatabaseFormat.CSV,
         out_path=None, out_fmt=OutputFormat.CSV,
@@ -343,8 +358,10 @@ def process_online_sessions(
                 time_from=time_from,
                 time_to=time_to)
 
+
 def main(args=None):
     process_online_sessions(**vars(_parse_args(args)))
 
+
 if __name__ == '__main__':
     main()
diff --git a/bin/show_status.py b/bin/show_status.py
index 1ca9cb5..cf59280 100644
--- a/bin/show_status.py
+++ b/bin/show_status.py
@@ -3,12 +3,14 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
-import argparse, sys
+import argparse
+import sys
 
 from vk.api import API
 from vk.tracking import StatusTracker
 from vk.tracking.db import Format as DatabaseFormat
 
+
 def _parse_args(args=None):
     if args is None:
         args = sys.argv[1:]
@@ -23,6 +25,7 @@ def _parse_args(args=None):
 
     return parser.parse_args(args)
 
+
 def track_status(uids, log_path=None):
     api = API()
     tracker = StatusTracker(api)
@@ -32,8 +35,10 @@ def track_status(uids, log_path=None):
         tracker.add_database_writer(log_writer)
         tracker.query_status(uids)
 
+
 def main(args=None):
     track_status(**vars(_parse_args(args)))
 
+
 if __name__ == '__main__':
     main()
diff --git a/bin/track_status.py b/bin/track_status.py
index 9c32ae9..2a974a5 100644
--- a/bin/track_status.py
+++ b/bin/track_status.py
@@ -3,15 +3,18 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
-import argparse, sys
+import argparse
+import sys
 
 from vk.api import API
 from vk.tracking import StatusTracker
 from vk.tracking.db import Format as DatabaseFormat
 
+
 DEFAULT_TIMEOUT = StatusTracker.DEFAULT_TIMEOUT
 DEFAULT_DB_FORMAT = DatabaseFormat.CSV
 
+
 def _parse_positive_integer(s):
     try:
         n = int(s)
@@ -21,12 +24,14 @@ def _parse_positive_integer(s):
         raise argparse.ArgumentTypeError('must be a positive integer: ' + s)
     return n
 
+
 def _parse_database_format(s):
     try:
         return DatabaseFormat(s)
     except ValueError:
         raise argparse.ArgumentTypeError('invalid database format: ' + s)
 
+
 def _parse_args(args=None):
     if args is None:
         args = sys.argv[1:]
@@ -52,6 +57,7 @@ def _parse_args(args=None):
 
     return parser.parse_args(args)
 
+
 def track_status(
         uids, timeout=DEFAULT_TIMEOUT,
         log_path=None,
@@ -72,8 +78,10 @@ def track_status(
 
             tracker.loop(uids)
 
+
 def main(args=None):
     track_status(**vars(_parse_args(args)))
 
+
 if __name__ == '__main__':
     main()
diff --git a/bin/utils/bar_chart.py b/bin/utils/bar_chart.py
index 522dfed..f051efc 100644
--- a/bin/utils/bar_chart.py
+++ b/bin/utils/bar_chart.py
@@ -7,6 +7,7 @@ import matplotlib.pyplot as plt
 from matplotlib import ticker
 import numpy as np
 
+
 class BarChartBuilder:
     _BAR_HEIGHT = .5
 
@@ -130,6 +131,7 @@ class BarChartBuilder:
     def save(self, path):
         self._fig.savefig(path, bbox_inches='tight')
 
+
 if __name__ == '__main__':
     import argparse
     parser = argparse.ArgumentParser()
diff --git a/bin/utils/io.py b/bin/utils/io.py
index 04baa6a..bb8eef9 100644
--- a/bin/utils/io.py
+++ b/bin/utils/io.py
@@ -8,6 +8,7 @@ import csv
 import json
 import sys
 
+
 class FileWriterJSON:
     def __init__(self, fd=sys.stdout):
         self._fd = fd
@@ -16,13 +17,14 @@ class FileWriterJSON:
         self._fd.write(json.dumps(something, indent=3, ensure_ascii=False))
         self._fd.write('\n')
 
+
 class FileWriterCSV:
     def __init__(self, fd=sys.stdout):
         self._writer = csv.writer(fd, lineterminator='\n')
 
     @staticmethod
     def _convert_row_old_python(row):
-        if isinstance(row, list) or isinstance(row, tuple):
+        if isinstance(row, (list, tuple)):
             return row
         return list(row)
 
@@ -31,6 +33,7 @@ class FileWriterCSV:
             row = self._convert_row_old_python(row)
         self._writer.writerow(row)
 
+
 @contextmanager
 def _open_file(path=None, default=None, **kwargs):
     if path is None:
@@ -39,8 +42,10 @@ def _open_file(path=None, default=None, **kwargs):
         with open(path, **kwargs) as fd:
             yield fd
 
+
 def open_output_text_file(path=None):
     return _open_file(path, default=sys.stdout, mode='w', encoding='utf-8')
 
+
 def open_output_binary_file(path=None):
     return _open_file(path, default=sys.stdout, mode='wb')
diff --git a/vk/api.py b/vk/api.py
index d79122d..0ba2f44 100644
--- a/vk/api.py
+++ b/vk/api.py
@@ -3,8 +3,7 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
-from collections import Iterable
-from collections.abc import Mapping
+from collections.abc import Iterable, Mapping
 from enum import Enum
 import json
 from urllib.error import URLError
@@ -14,21 +13,24 @@ from urllib.request import urlopen
 import vk.error
 from vk.user import User
 
+
 def _split_url(url):
     return urllib.parse.urlsplit(url)[:3]
 
+
 def _is_empty_param_value(value):
     return isinstance(value, str) and not value
 
+
 def _filter_empty_params(params, empty_params=False):
     if empty_params:
         return params
     if isinstance(params, Mapping):
         return {name: value for name, value in params.items() if not _is_empty_param_value(value)}
-    elif isinstance(params, Iterable):
+    if isinstance(params, Iterable):
         return [(name, value) for name, value in params if not _is_empty_param_value(value)]
-    else:
-        raise TypeError()
+    raise TypeError()
+
 
 def _build_url(scheme, host, path, params=None, empty_params=False):
     if params is None:
@@ -43,6 +45,7 @@ def _build_url(scheme, host, path, params=None, empty_params=False):
     path = urllib.parse.quote(path)
     return urllib.parse.urlunsplit((scheme, host, path, params, ''))
 
+
 def _join_param_values(values):
     if isinstance(values, str):
         return values
@@ -50,13 +53,16 @@ def _join_param_values(values):
         return ','.join(map(str, values))
     return values
 
+
 def _join_path(base, url):
     if not base.endswith('/'):
         base += '/'
     return urllib.parse.urljoin(base, url)
 
+
 ACCESS_TOKEN = '9722cef09722cef09722cef071974b8cbe997229722cef0cbabfd816916af6c7bd37006'
 
+
 class Version(Enum):
     V5_73 = '5.73'
     DEFAULT = V5_73
@@ -64,6 +70,7 @@ class Version(Enum):
     def __str__(self):
         return self.value
 
+
 class Language(Enum):
     EN = 'en'
     DEFAULT = EN
@@ -71,6 +78,7 @@ class Language(Enum):
     def __str__(self):
         return self.value
 
+
 class Method(Enum):
     USERS_GET = 'users.get'
     FRIENDS_GET = 'friends.get'
@@ -78,6 +86,7 @@ class Method(Enum):
     def __str__(self):
         return self.value
 
+
 class CommonParameters(Enum):
     ACCESS_TOKEN = 'access_token'
     VERSION = 'v'
@@ -86,6 +95,7 @@ class CommonParameters(Enum):
     def __str__(self):
         return self.value
 
+
 class API:
     _ROOT_URL = 'https://api.vk.com/method/'
 
@@ -136,4 +146,5 @@ class API:
             fields=_join_param_values(fields))
         if 'items' not in response:
             raise vk.error.InvalidAPIResponseError(response)
-        return self._filter_response_with_users(response['items'], deactivated_users)
+        return self._filter_response_with_users(response['items'],
+                                                deactivated_users)
diff --git a/vk/error.py b/vk/error.py
index 3a309c3..5f71e47 100644
--- a/vk/error.py
+++ b/vk/error.py
@@ -3,9 +3,11 @@
 # For details, see https://github.com/egor-tensin/vk-scripts.
 # Distributed under the MIT License.
 
+
 class APIError(RuntimeError):
     pass
 
+
 class InvalidAPIResponseError(APIError):
     def __init__(self, response):
         super().__init__()
@@ -14,5 +16,6 @@ class InvalidAPIResponseError(APIError):
     def __str__(self):
         return str(self.response)
 
+
 class APIConnectionError(APIError):
     pass
diff --git a/vk/last_seen.py b/vk/last_seen.py
index 25975f2..cf76db5 100644
--- a/vk/last_seen.py
+++ b/vk/last_seen.py
@@ -11,6 +11,7 @@ from numbers import Integral, Real
 
 from .platform import Platform
 
+
 def _parse_time(x):
     if isinstance(x, datetime):
         if x.tzinfo is None or x.tzinfo.utcoffset(x) is None:
@@ -20,6 +21,7 @@ def _parse_time(x):
         return datetime.fromtimestamp(x, tz=timezone.utc)
     raise TypeError()
 
+
 def _parse_platform(x):
     if x in Platform:
         return x
@@ -27,6 +29,7 @@ def _parse_platform(x):
         return Platform.from_string(x)
     return Platform(x)
 
+
 class LastSeenField(Enum):
     TIME = 'time'
     PLATFORM = 'platform'
@@ -34,6 +37,7 @@ class LastSeenField(Enum):
     def __str__(self):
         return self.value
 
+
 class LastSeen(MutableMapping):
     @staticmethod
     def from_api_response(source):
diff --git a/vk/platform.py b/vk/platform.py
index 8bf23c5..5cd78b8 100644
--- a/vk/platform.py
+++ b/vk/platform.py
@@ -6,6 +6,7 @@
 from enum import Enum
 import re
 
+
 class Platform(Enum):
     MOBILE = 1
     IPHONE = 2
@@ -43,6 +44,7 @@ class Platform(Enum):
     def get_descr_text_capitalized(self):
         return self._capitalize_first_letter(self.get_descr_text())
 
+
 _PLATFORM_DESCRIPTIONS = {
     Platform.MOBILE: '"mobile" web version (or unrecognized mobile app)',
     Platform.IPHONE: 'official iPhone app',
diff --git a/vk/tracking/db/backend/csv.py b/vk/tracking/db/backend/csv.py
index 4943ff2..43038e4 100644
--- a/vk/tracking/db/backend/csv.py
+++ b/vk/tracking/db/backend/csv.py
@@ -8,6 +8,7 @@ from ..io import FileReaderCSV, FileWriterCSV
 from ..record import Record
 from ..timestamp import Timestamp
 
+
 class Writer(meta.Writer):
     def __init__(self, fd):
         self._writer = FileWriterCSV(fd)
@@ -30,6 +31,7 @@ class Writer(meta.Writer):
     def _record_to_row(record):
         return [str(record.get_timestamp())] + [str(record[field]) for field in record]
 
+
 class Reader(meta.Reader):
     def __init__(self, fd):
         self._reader = FileReaderCSV(fd)
diff --git a/vk/tracking/db/backend/log.py b/vk/tracking/db/backend/log.py
index 814cabc..d301856 100644
--- a/vk/tracking/db/backend/log.py
+++ b/vk/tracking/db/backend/log.py
@@ -7,6 +7,7 @@ import logging
 
 from .. import meta
 
+
 class Writer(meta.Writer):
     def __init__(self, fd):
         self._logger = logging.getLogger(__file__)
diff --git a/vk/tracking/db/backend/null.py b/vk/tracking/db/backend/null.py
index 663af10..80a66b4 100644
--- a/vk/tracking/db/backend/null.py
+++ b/vk/tracking/db/backend/null.py
@@ -5,6 +5,7 @@
 
 from .. import meta
 
+
 class Writer(meta.Writer):
     def __init__(self):
         pass
@@ -18,6 +19,7 @@ class Writer(meta.Writer):
     def on_connection_error(self, e):
         pass
 
+
 class Reader(meta.Reader):
     def __init__(self):
         pass
diff --git a/vk/tracking/db/format.py b/vk/tracking/db/format.py
index f9a670c..028d403 100644
--- a/vk/tracking/db/format.py
+++ b/vk/tracking/db/format.py
@@ -8,6 +8,7 @@ import sys
 
 from . import backend, io
 
+
 class Format(Enum):
     CSV = 'csv'
     LOG = 'log'
@@ -19,22 +20,20 @@ class Format(Enum):
     def create_writer(self, fd=sys.stdout):
         if self is Format.CSV:
             return backend.csv.Writer(fd)
-        elif self is Format.LOG:
+        if self is Format.LOG:
             return backend.log.Writer(fd)
-        elif self is Format.NULL:
+        if self is Format.NULL:
             return backend.null.Writer()
-        else:
-            raise NotImplementedError('unsupported database format: ' + str(self))
+        raise NotImplementedError('unsupported database format: ' + str(self))
 
     def open_output_file(self, path=None):
         if self is Format.CSV:
             return self._open_output_database_file(path)
-        elif self is Format.LOG:
+        if self is Format.LOG:
             return self._open_output_log_file(path)
-        elif self is Format.NULL:
+        if self is Format.NULL:
             return self._open_output_database_file(None)
-        else:
-            raise NotImplementedError('unsupported database format: ' + str(self))
+        raise NotImplementedError('unsupported database format: ' + str(self))
 
     @staticmethod
     def _open_output_log_file(path):
@@ -47,19 +46,17 @@ class Format(Enum):
     def create_reader(self, fd=sys.stdin):
         if self is Format.CSV:
             return backend.csv.Reader(fd)
-        elif self is Format.LOG:
+        if self is Format.LOG:
             return NotImplementedError('cannot read from a log file')
-        elif self is Format.NULL:
+        if self is Format.NULL:
             return backend.null.Reader()
-        else:
-            raise NotImplementedError('unsupported database format: ' + str(self))
+        raise NotImplementedError('unsupported database format: ' + str(self))
 
     def open_input_file(self, path=None):
         if self is Format.CSV:
             return io.open_input_text_file(path)
-        elif self is Format.LOG:
+        if self is Format.LOG:
             raise NotImplementedError('cannot read from a log file')
-        elif self is Format.NULL:
+        if self is Format.NULL:
             return io.open_input_text_file(None)
-        else:
-            raise NotImplementedError('unsupported database format: ' + str(self))
+        raise NotImplementedError('unsupported database format: ' + str(self))
diff --git a/vk/tracking/db/io.py b/vk/tracking/db/io.py
index 37d9c53..a89865f 100644
--- a/vk/tracking/db/io.py
+++ b/vk/tracking/db/io.py
@@ -7,6 +7,7 @@ from contextlib import contextmanager
 import csv
 import sys
 
+
 class FileWriterCSV:
     def __init__(self, fd=sys.stdout):
         self._fd = fd
@@ -14,7 +15,7 @@ class FileWriterCSV:
 
     @staticmethod
     def _convert_row_old_python(row):
-        if isinstance(row, list) or isinstance(row, tuple):
+        if isinstance(row, (list, tuple)):
             return row
         return list(row)
 
@@ -24,6 +25,7 @@ class FileWriterCSV:
         self._writer.writerow(row)
         self._fd.flush()
 
+
 class FileReaderCSV:
     def __init__(self, fd=sys.stdin):
         self._reader = csv.reader(fd)
@@ -31,6 +33,7 @@ class FileReaderCSV:
     def __iter__(self):
         return iter(self._reader)
 
+
 @contextmanager
 def _open_file(path=None, default=None, **kwargs):
     if path is None:
@@ -39,12 +42,15 @@ def _open_file(path=None, default=None, **kwargs):
         with open(path, **kwargs) as fd:
             yield fd
 
+
 _DEFAULT_ENCODING = 'utf-8'
 
+
 def open_output_text_file(path=None, mode='w'):
     return _open_file(path, default=sys.stdout, mode=mode,
                       encoding=_DEFAULT_ENCODING)
 
+
 def open_input_text_file(path=None):
     return _open_file(path, default=sys.stdin, mode='r',
                       encoding=_DEFAULT_ENCODING)
diff --git a/vk/tracking/db/meta.py b/vk/tracking/db/meta.py
index 024d9d8..eb15c74 100644
--- a/vk/tracking/db/meta.py
+++ b/vk/tracking/db/meta.py
@@ -6,6 +6,7 @@
 import abc
 from collections.abc import Iterable
 
+
 class Writer(metaclass=abc.ABCMeta):
     @abc.abstractmethod
     def on_initial_status(self, user):
@@ -19,6 +20,7 @@ class Writer(metaclass=abc.ABCMeta):
     def on_connection_error(self, e):
         pass
 
+
 class Reader(Iterable, metaclass=abc.ABCMeta):
     @abc.abstractmethod
     def __iter__(self):
diff --git a/vk/tracking/db/record.py b/vk/tracking/db/record.py
index dfd47c6..6998238 100644
--- a/vk/tracking/db/record.py
+++ b/vk/tracking/db/record.py
@@ -12,6 +12,7 @@ from vk.user import User, UserField
 
 from .timestamp import Timestamp
 
+
 class Record(MutableMapping):
     FIELDS = (
         UserField.UID,
diff --git a/vk/tracking/db/timestamp.py b/vk/tracking/db/timestamp.py
index b2219ca..1309797 100644
--- a/vk/tracking/db/timestamp.py
+++ b/vk/tracking/db/timestamp.py
@@ -5,6 +5,7 @@
 
 from datetime import datetime, timezone
 
+
 class Timestamp:
     @staticmethod
     def _new():
diff --git a/vk/tracking/online_sessions.py b/vk/tracking/online_sessions.py
index 204e1cc..c43e11c 100644
--- a/vk/tracking/online_sessions.py
+++ b/vk/tracking/online_sessions.py
@@ -8,6 +8,7 @@ from collections.abc import MutableMapping
 from datetime import timedelta
 from enum import Enum
 
+
 class Weekday(Enum):
     MONDAY = 0
     TUESDAY = 1
@@ -20,6 +21,7 @@ class Weekday(Enum):
     def __str__(self):
         return self.name[0] + self.name[1:].lower()
 
+
 class OnlineSessionEnumerator(MutableMapping):
     def __init__(self, time_from=None, time_to=None):
         self._records = {}
diff --git a/vk/tracking/status_tracker.py b/vk/tracking/status_tracker.py
index 30e0f97..b87e059 100644
--- a/vk/tracking/status_tracker.py
+++ b/vk/tracking/status_tracker.py
@@ -11,6 +11,7 @@ import signal
 import vk.error
 from vk.user import UserField
 
+
 class StatusTracker:
     DEFAULT_TIMEOUT = 5
 
@@ -49,7 +50,8 @@ class StatusTracker:
     _USER_FIELDS = UserField.DOMAIN, UserField.ONLINE, UserField.LAST_SEEN,
 
     def _query_status(self, uids):
-        user_list = self._api.users_get(uids, self._USER_FIELDS, deactivated_users=False)
+        user_list = self._api.users_get(uids, self._USER_FIELDS,
+                                        deactivated_users=False)
         return {user.get_uid(): user for user in user_list}
 
     def _notify_status(self, user):
diff --git a/vk/user.py b/vk/user.py
index c3c997b..eb65eaf 100644
--- a/vk/user.py
+++ b/vk/user.py
@@ -9,31 +9,33 @@ from enum import Enum
 
 from .last_seen import LastSeen
 
+
 def _parse_last_seen(x):
     if isinstance(x, LastSeen):
         return x
-    elif isinstance(x, Mapping):
+    if isinstance(x, Mapping):
         return LastSeen.from_api_response(x)
-    else:
-        raise TypeError()
+    raise TypeError()
+
 
 def _parse_bool(x):
     if isinstance(x, str):
         if str(True) == x:
             return True
-        elif str(False) == x:
+        if str(False) == x:
             return False
-        else:
-            raise ValueError()
-    else:
-        return bool(x)
+        raise ValueError()
+    return bool(x)
+
 
 def _parse_hidden(x):
     return _parse_bool(x)
 
+
 def _parse_online_flag(x):
     return _parse_bool(x)
 
+
 class UserField(Enum):
     UID = 'id'
     FIRST_NAME = 'first_name'
@@ -48,6 +50,7 @@ class UserField(Enum):
     def __str__(self):
         return self.value
 
+
 class DeactivationReason(Enum):
     DELETED = 'deleted'
     BANNED = 'banned'
@@ -55,9 +58,11 @@ class DeactivationReason(Enum):
     def __str__(self):
         return self.value
 
+
 def _parse_deactivated(s):
     return DeactivationReason(s)
 
+
 class User(Hashable, MutableMapping):
     @staticmethod
     def from_api_response(source):