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Mini Shell
import csv
import datetime
from decimal import Decimal
import json
import operator
try:
from urlparse import urlparse
except ImportError:
from urllib.parse import urlparse
import sys
from peewee import *
from playhouse.db_url import connect
from playhouse.migrate import migrate
from playhouse.migrate import SchemaMigrator
from playhouse.reflection import Introspector
if sys.version_info[0] == 3:
basestring = str
from functools import reduce
class DataSet(object):
def __init__(self, url):
self._url = url
parse_result = urlparse(url)
self._database_path = parse_result.path[1:]
# Connect to the database.
self._database = connect(url)
self._database.connect()
# Introspect the database and generate models.
self._introspector = Introspector.from_database(self._database)
self._models = self._introspector.generate_models(skip_invalid=True)
self._migrator = SchemaMigrator.from_database(self._database)
class BaseModel(Model):
class Meta:
database = self._database
self._base_model = BaseModel
self._export_formats = self.get_export_formats()
self._import_formats = self.get_import_formats()
def __repr__(self):
return '<DataSet: %s>' % self._database_path
def get_export_formats(self):
return {
'csv': CSVExporter,
'json': JSONExporter}
def get_import_formats(self):
return {
'csv': CSVImporter,
'json': JSONImporter}
def __getitem__(self, table):
return Table(self, table, self._models.get(table))
@property
def tables(self):
return self._database.get_tables()
def __contains__(self, table):
return table in self.tables
def connect(self):
self._database.connect()
def close(self):
self._database.close()
def update_cache(self, table=None):
if table:
model_class = self._models[table]
dependencies = model_class._meta.related_models(backrefs=True)
else:
dependencies = None # Update all tables.
updated = self._introspector.generate_models(
skip_invalid=True,
table_names=[related._meta.db_table for related in dependencies])
self._models.update(updated)
def __enter__(self):
self.connect()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
if not self._database.is_closed():
self.close()
def query(self, sql, params=None, commit=True):
return self._database.execute_sql(sql, params, commit)
def transaction(self):
if self._database.transaction_depth() == 0:
return self._database.transaction()
else:
return self._database.savepoint()
def _check_arguments(self, filename, file_obj, format, format_dict):
if filename and file_obj:
raise ValueError('file is over-specified. Please use either '
'filename or file_obj, but not both.')
if not filename and not file_obj:
raise ValueError('A filename or file-like object must be '
'specified.')
if format not in format_dict:
valid_formats = ', '.join(sorted(format_dict.keys()))
raise ValueError('Unsupported format "%s". Use one of %s.' % (
format, valid_formats))
def freeze(self, query, format='csv', filename=None, file_obj=None,
**kwargs):
self._check_arguments(filename, file_obj, format, self._export_formats)
if filename:
file_obj = open(filename, 'w')
exporter = self._export_formats[format](query)
exporter.export(file_obj, **kwargs)
if filename:
file_obj.close()
def thaw(self, table, format='csv', filename=None, file_obj=None,
strict=False, **kwargs):
self._check_arguments(filename, file_obj, format, self._export_formats)
if filename:
file_obj = open(filename, 'r')
importer = self._import_formats[format](self[table], strict)
count = importer.load(file_obj, **kwargs)
if filename:
file_obj.close()
return count
class Table(object):
def __init__(self, dataset, name, model_class):
self.dataset = dataset
self.name = name
if model_class is None:
model_class = self._create_model()
model_class.create_table()
self.dataset._models[name] = model_class
@property
def model_class(self):
return self.dataset._models[self.name]
def __repr__(self):
return '<Table: %s>' % self.name
def __len__(self):
return self.find().count()
def __iter__(self):
return iter(self.find().iterator())
def _create_model(self):
class Meta:
db_table = self.name
return type(
str(self.name),
(self.dataset._base_model,),
{'Meta': Meta})
def create_index(self, columns, unique=False):
self.dataset._database.create_index(
self.model_class,
columns,
unique=unique)
def _guess_field_type(self, value):
if isinstance(value, basestring):
return TextField
if isinstance(value, (datetime.date, datetime.datetime)):
return DateTimeField
elif value is True or value is False:
return BooleanField
elif isinstance(value, int):
return IntegerField
elif isinstance(value, float):
return FloatField
elif isinstance(value, Decimal):
return DecimalField
return TextField
@property
def columns(self):
return [f.name for f in self.model_class._meta.sorted_fields]
def _migrate_new_columns(self, data):
new_keys = set(data) - set(self.model_class._meta.fields)
if new_keys:
operations = []
for key in new_keys:
field_class = self._guess_field_type(data[key])
field = field_class(null=True)
operations.append(
self.dataset._migrator.add_column(self.name, key, field))
field.add_to_class(self.model_class, key)
migrate(*operations)
self.dataset.update_cache(self.name)
def insert(self, **data):
self._migrate_new_columns(data)
return self.model_class.insert(**data).execute()
def _apply_where(self, query, filters, conjunction=None):
conjunction = conjunction or operator.and_
if filters:
expressions = [
(self.model_class._meta.fields[column] == value)
for column, value in filters.items()]
query = query.where(reduce(conjunction, expressions))
return query
def update(self, columns=None, conjunction=None, **data):
self._migrate_new_columns(data)
filters = {}
if columns:
for column in columns:
filters[column] = data.pop(column)
return self._apply_where(
self.model_class.update(**data),
filters,
conjunction).execute()
def _query(self, **query):
return self._apply_where(self.model_class.select(), query)
def find(self, **query):
return self._query(**query).dicts()
def find_one(self, **query):
try:
return self.find(**query).get()
except self.model_class.DoesNotExist:
return None
def all(self):
return self.find()
def delete(self, **query):
return self._apply_where(self.model_class.delete(), query).execute()
def freeze(self, *args, **kwargs):
return self.dataset.freeze(self.all(), *args, **kwargs)
def thaw(self, *args, **kwargs):
return self.dataset.thaw(self.name, *args, **kwargs)
class Exporter(object):
def __init__(self, query):
self.query = query
def export(self, file_obj):
raise NotImplementedError
class JSONExporter(Exporter):
@staticmethod
def default(o):
if isinstance(o, (datetime.datetime, datetime.date, datetime.time)):
return o.isoformat()
elif isinstance(o, Decimal):
return str(o)
raise TypeError('Unable to serialize %r as JSON.' % o)
def export(self, file_obj, **kwargs):
json.dump(
list(self.query),
file_obj,
default=JSONExporter.default,
**kwargs)
class CSVExporter(Exporter):
def export(self, file_obj, header=True, **kwargs):
writer = csv.writer(file_obj, **kwargs)
if header and hasattr(self.query, '_select'):
writer.writerow([field.name for field in self.query._select])
for row in self.query.tuples():
writer.writerow(row)
class Importer(object):
def __init__(self, table, strict=False):
self.table = table
self.strict = strict
model = self.table.model_class
self.columns = model._meta.columns
self.columns.update(model._meta.fields)
def load(self, file_obj):
raise NotImplementedError
class JSONImporter(Importer):
def load(self, file_obj, **kwargs):
data = json.load(file_obj, **kwargs)
count = 0
for row in data:
if self.strict:
obj = {}
for key in row:
field = self.columns.get(key)
if field is not None:
obj[field.name] = field.python_value(row[key])
else:
obj = row
if obj:
self.table.insert(**obj)
count += 1
return count
class CSVImporter(Importer):
def load(self, file_obj, header=True, **kwargs):
count = 0
reader = csv.reader(file_obj, **kwargs)
if header:
try:
header_keys = next(reader)
except StopIteration:
return count
if self.strict:
header_fields = []
for idx, key in enumerate(header_keys):
if key in self.columns:
header_fields.append((idx, self.columns[key]))
else:
header_fields = list(enumerate(header_keys))
else:
header_fields = list(enumerate(self.model._meta.sorted_fields))
if not header_fields:
return count
for row in reader:
obj = {}
for idx, field in header_fields:
if self.strict:
obj[field.name] = field.python_value(row[idx])
else:
obj[field] = row[idx]
self.table.insert(**obj)
count += 1
return count
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