我正在使用带有sqlalchemy的PostGreSQL。我对数据库比较陌生,对sqlalchemy来说是全新的。我目前有一个简单的数据库,其中包含githash(主键),提交者和日期的列。
我有一个收集数据的JSON文件,我的主要目标是将所有数据从文件传输到数据库(所有新数据也将被放入数据库)。我编写的python脚本允许传入json文件的参数(-j)和文件路径以添加到数据库中;但是不需要它,因为一旦数据在数据库中,我希望能够从数据库中获取数据而不指定JSON文件。
这是我的问题所在。当我指定JSON文件时,如下所示:
python PostGreSQLTest.py -j JSONFile.json
1012
从数据库中添加1012行,然后再提取,数据库GUI也反映了这一点。
紧接着之后,我在没有JSON文件的情况下调用脚本,并尝试从数据库中获取行数,它显示0行(作为脚本输出和GUI内的输出。)
python PostGreSQLTest.py
0
似乎数据在会话之间没有持久存储在数据库中,即使我确实调用了session.commit()。我已经包含了以下代码的示例。任何对这个问题的见解都将非常感激。
from argparse import ArgumentParser
import json
import os
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Text, Integer, Date, create_engine, ForeignKey
from sqlalchemy.orm import scoped_session, sessionmaker
Base = declarative_base()
session = scoped_session(sessionmaker())
class TestRecord(Base):
__tablename__ = 'test_table'
githash = Column(Text, primary_key=True)
committer = Column(Text)
date = Column(Date)
class TestDatabase(object):
'''
classdocs
'''
def __init__(self):
'''
Constructor
'''
self.db_name = "test_db"
self.user = "un"
self.pw = "pw"
engine = self.__init_db()
'''Initializers'''
def __init_db(self):
engine_string = 'postgresql://{0}:{1}@localhost/{2}'.format(self.user, self.pw, self.db_name)
engine = create_engine(engine_string, echo=False)
session.remove()
session.configure(bind=engine, autoflush=False, expire_on_commit=False)
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
return engine
def __grab_json_file(self, filename):
jsonFile = open(filename, 'rb')
J = json.load(jsonFile)
jsonFile.close()
return J
'''Helper Functions'''
'''Main Functions'''
def add_entries_from_JSON(self, filename):
'''
Add Entries From JSON reads in a JSON file and creates records in the database.
:param filename: <String> Full path to the JSON File
:return success: <bool> True if records are successfully written, False otherwise
'''
TR_entries = []
success = False
if os.path.isfile(filename):
# If the JSON file exists, open it and create records
entries = self.__grab_json_file(filename)
for key in entries.keys():
TR = TestRecord()
TR.githash = entries[key]["gitHash"]
TR.date = entries[key]["Date"]
TR.committer = entries[key]["Committer"]
TR_entries.append(TR)
# Add all records from the list of TestRecord objects to the database
success = self.add_multiple_entries(TR_entries)
else:
print "JSON file '{0}' provided does not exist.".format(filename)
return success
def add_multiple_entries(self, entries):
'''
Add multiple entries adds multiple entries to the database.
:param entries: <list of TestRecord> list of records to add to the database
:return success: <bool> True if successfully added, false otherwise
'''
success = True
try:
session.add_all(entries)
session.commit()
except:
success = False
raise
return success
def get_num_rows(self):
'''
Get the number of rows in the database.
:return numRows: the number of rows in the database
'''
numRows = session.query(TestRecord).count()
return numRows
def cleanup(self):
'''
Cleanup wraps everything up.
'''
session.close()
def main (jsonFile=None):
TD = TestDatabase()
if jsonFile is not None:
if TD.add_entries_from_JSON(jsonFile) is False:
print "Failed to add entries from JSON File '{0}'.".format(jsonFile)
rows = TD.get_num_rows()
print rows
TD.cleanup()
def argparser():
argparser = ArgumentParser( description = 'PostGreSQL Database operations.' )
argparser.add_argument('-j',
'--jsonFile',
help='Full file path to a JSON file containing databse entries.',
required = False
)
return argparser
if __name__ == "__main__":
args = argparser().parse_args()
main(args.jsonFile)
答案 0 :(得分:0)
数据在会话之间不会持久存储在数据库中,
呃......你是说你的脚本单独调用之间没有数据?放弃所有表格时会出现这种情况:
def __init_db(self):
# ... snip ...
Base.metadata.drop_all(engine)
# ^^^^^^^^
Base.metadata.create_all(engine)
摆脱那条线。如果没有&#34;放弃一切,它应该做什么!&#34;