Develop Reference

Python unitest mock to check that a method returns a method call

I'm trying to figure out how I can simply check that the execute_db returns
a method call with the name cursor.fetchone?
I'm not interested to see if the db works, that will be done in a integration test later on.
I've written a small unittest already, but here I'm only mocking the return value.. I want to find a way to test that the method with the given name is being called as well.
class DataChecker:
def __init__(self):
# Initialize class
self.conn = sqlite3.connect("pos.db")
self.cursor = self.conn.cursor()
def execute_db(self, query, params=None):
# Execute SQL query with parameters and return data
self.cursor.execute(query, [params])
self.conn.commit()
return self.cursor.fetchone()
Test:
def test_execute_db():
mock_datachecker = Mock()
mock_datachecker.cursor.fetchone.return_value = "one"
assert DataChecker.execute_db(mock_datachecker, "SELECT * FROM Customers;", 1) == "one"

You would mock the method fetchone from sqlite3 that is imported in DataChecker module.
db.py
import sqlite3
class DataChecker:
def __init__(self):
# Initialize class
self.conn = sqlite3.connect("pos.db")
self.cursor = self.conn.cursor()
def execute_db(self, query, params=None):
# Execute SQL query with parameters and return data
if params:
self.cursor.execute(query, params)
else:
self.cursor.execute(query)
self.conn.commit()
return self.cursor.fetchone()
Then you could use the db.sqlite3 to mock the connect().cursor().fetchone method.
def test_execute_db():
with patch('db.sqlite3') as mock_db:
mock_db.connect().cursor().fetchone.return_value = "one"
assert DataChecker().execute_db("SELECT * FROM Customers") == "one"

Use decorator to connect to a postgres database

I am working on a program to store my picture meta data and thumbnails into a postgres database using python and psycopg2. In the example I have defined a class MyDbase with methods to create a table, store a value and load a value. Each of these methods needs to connect to the database and a cursor object to execute sql commands. To avoid repetition of code to make the connection and get the cursor I have made a sub class DbDecorators with a decorator connect.
My question: is this a proper way to handle this and specifically using the with statement and passing the cursor to the Dbase method (func) inside the wrapper?
from functools import wraps
import psycopg2
class MyDbase:
''' example using a decorator to connect to a dbase
'''
table_name = 'my_table'
class DbDecorators:
host = 'localhost'
db_user = 'db_tester'
db_user_pw = 'db_tester_pw'
database = 'my_database'
#classmethod
def connect(cls, func):
#wraps(func)
def wrapper(*args, **kwargs):
connect_string = f'host=\'{cls.host}\' dbname=\'{cls.database}\''\
f'user=\'{cls.db_user}\' password=\'{cls.db_user_pw}\''
result = None
try:
with psycopg2.connect(connect_string) as connection:
cursor = connection.cursor()
result = func(*args, cursor, **kwargs)
except psycopg2.Error as error:
print(f'error while connect to PostgreSQL {cls.database}: '
f'{error}')
finally:
if connection:
cursor.close()
connection.close()
print(f'PostgreSQL connection to {cls.database} is closed')
return result
return wrapper
#staticmethod
def get_cursor(cursor):
if cursor:
return cursor
else:
print(f'no connection to database')
raise()
#classmethod
#DbDecorators.connect
def create_table(cls, *args):
cursor = cls.DbDecorators().get_cursor(*args)
sql_string = f'CREATE TABLE {cls.table_name} '\
f'(id SERIAL PRIMARY KEY, name VARCHAR(30));'
print(sql_string)
cursor.execute(sql_string)
#classmethod
#DbDecorators.connect
def store_value(cls, name, *args):
cursor = cls.DbDecorators().get_cursor(*args)
sql_string = f'INSERT INTO {cls.table_name} (name) VALUES (%s);'
print(sql_string)
cursor.execute(sql_string, (name,))
#classmethod
#DbDecorators.connect
def load_value(cls, _id, *args):
cursor = cls.DbDecorators().get_cursor(*args)
sql_string = f'SELECT * FROM {cls.table_name} where id = \'{_id}\';'
print(sql_string)
cursor.execute(sql_string)
db_row = cursor.fetchone()
return db_row
def test():
my_db = MyDbase()
my_db.create_table()
my_db.store_value('John Dean')
db_row = my_db.load_value(1)
print(f'id: {db_row[0]}, name: {db_row[1]}')
if __name__ == '__main__':
test()

probably I did not get your request correctly. Why you need decorator but don't use context manager? Like define db client in any file where from you can import it later and then use it in context manager –
from psycopg2 import SomeDataBase
db = SomeDataBase(credentials)
def create_table(table_name):
with db:
sql_string = f'CREATE TABLE {table_name} '\
f'(id SERIAL PRIMARY KEY, name VARCHAR(30));'
db.cursor.execute(sql_string)

Using a context manager will not close the connection, only the cursor. So using the decorator pattern actually makes more sense here. More info on the context manager: https://www.psycopg.org/docs/usage.html (scroll down to the "with statement" section.)

Calling method to another method in python

I have lots of database queries and I would like to use some methods to not repeat my code. I would like to call methods in other defined methods but it doesn't work
I'm getting such error:
class Main:
File "d.py", line 20, in Main
for word in getUserWords("SELECT users.mail, field_data_field_what_word_are_you_looking_.field_what_word_are_you_looking__value, users.uid FROM users INNER JOIN field_data_field_what_word_are_you_looking_ ON users.uid = field_data_field_what_word_are_you_looking_.entity_id"):
TypeError: getUserWords() takes exactly 2 arguments (1 given)
my code
import MySQLdb as mdb
Class Main:
def connect(self):
con = mdb.connect('***', '*****', '****', '***', charset="utf8", use_unicode=True)
return con
def cursor(self):
cursor = self.connect.cursor()
return cursor()
def getUserWords(self, sql):
self.sql = sql
self.cursor.execute(self.sql)
data = self.cursor.fetchall()
self.connect.commit()
self.connect.close()
return data
for word in getUserWords("SELECT users.mail, field_data_field_what_word_are_you_looking_.field_what_word_are_you_looking__value, users.uid FROM users INNER JOIN field_data_field_what_word_are_you_looking_ ON users.uid = field_data_field_what_word_are_you_looking_.entity_id"):
print word

Simpler example:
class Foo(object):
def __init__(self):
self.foo = "bar"
def function1(self,x):
self.function2(x)
def function2(self,y):
print y
bar = Foo()
bar.function1(3) # calls function1 which in turn calls function2 which prints out 3
bar.function2(4) # calls function 2 directly.
The main takeaway to answer your question:
If you have a class function, it has a first argument which is by convention self. If you call that class function on an instance (as in bar.function2), the self is implicit. If you call that class function from within the class (as when function1 calls function2), you need to do self.functionname, which again implicitly passes the self argument.

First point: instanciate your class and call getUserWords() on your instance:
import MySQLdb as mdb
class Main:
# snip
m = Main()
sql = your_sql_here
for word in m.getUserWords(sql):
print word
Second point: your implementation of Main is flawed.
Class Main:
def connect(self):
# this will open a new connection on each and every call
con = mdb.connect('***', '*****', '****', '***', charset="utf8", use_unicode=True)
return con
def cursor(self):
# this will
# 1. create a new connection on every call - which will
# never be closed since you don't keep a reference
# on it so you can close it
# 2. create a new cursor on every call
cursor = self.connect.cursor()
# and this one will raise a TypeError
# => "'Cursor' object is not callable"
return cursor()
# so I assume your real code is :
return cursor
def getUserWords(self, sql):
# assigning sql to self is totally useless here
self.sql = sql
# so (assuming self.cursor returns the cursor and not
# the call to the cursor), this will:
# - open a new connection
# - create a new cursor
# - execute the sql
# - and discards eveything (cursor and connection)
# without closing them
self.cursor.execute(self.sql)
# now we
# - open a second connection (without closing the first)
# - create a second cursor
# - call .fetchall() on it, which will raise a
# _mysql_exceptions.ProgrammingError
data = self.cursor.fetchall()
# we're not making it until this part because of
# the above error, but if we did, this would:
# - create yet a third connection and call .commit()
# on it - which in this case would mainly be a no-op
# since we have nothing to commit
self.connect.commit()
# and finally create a fourth connection and close it
# immediatly - note that this will be the only one that
# gets closed <g>
self.connect.close()
return data
A fixed version of your code could look something like this:
import MySQLdb as mdb
class Main(object):
def __init__(self, connection_data):
self._connection_data = connection_data.copy()
self._connection_data.update(charset="utf8", use_unicode=True)
self._db = None
#property
def db(self):
if self._db is None:
self._db = mdb.connect(**self._connection_data)
return self._db
def cursor(self):
return self.db.cursor()
def execute(self, sql):
cursor = self.cursor()
cursor.execute(self.sql)
for row in cursor:
yield row
self.db.commit()
cursor.close()
def __del__(self):
try:
self._db.close()
except:
# either it's not set or it's already closed
pass
m = Main(db="***", user="***", passwd="***")
for w in m.getUserWords(your_sql_here):
print w

sqlite3.Connection class inheritance, commit not working

This is my first time using sqlite3 through class inheritance, and I've run into a problem where I get no traceback errors, but the queries I execute won't commit. I simplified my code
import sqlite3 as lite
class BaseModel(lite.Connection):
def __init__(self, **args):
lite.Connection.__init__(self, **args)
self.cur = self.cursor()
def execute(self, query):
self.cur.execute(query)
class Model(BaseModel):
def __init__(self, **args):
BaseModel.__init__(self, **args)
def _new_(self):
queries = []
queries.append(' '.join(['CREATE TABLE IF NOT EXISTS tb1',
'(id INTEGER PRIMARY KEY,',
'column1 TEXT,',
'column2 INT)']))
for q in queries:
self.execute(q) # execute the queries
self.commit() # write changes to db
def tables(self):
query = 'SELECT name FROM sqlite_master WHERE type="table" ORDER BY name'
results = self.execute(query)
return results#.fetchall()
if __name__ == '__main__':
model = Model(database='test.db')
model._new_()
# Test Fails because the queries aren't being saved in the db
# see Model.__new__ for details
tables = model.tables() # get all tables
print 'Tables Created:'
if tables:
for t in model.tables():
print '\t%s' % str(t[0])
else: print tables

You need to call self.commit():
self.commit() # write changes to db
Without the () you are merely referencing the method, not invoking it.
Next, your execute() function doesn't return anything:
def execute(self, query):
return self.cur.execute(query)

Create an instance of a class from SQL query

I have the following class:
class SomeClass:
def __init__(self, name, date):
self.name = name
self.date = date
Now I have a function in another module, which connects to a SQLite database and executes a query:
def getEntry(user):
data = []
connection = lite.connect(database)
with connection:
cur = connection.cursor()
cur.execute("SELECT name, date FROM table WHERE column = ?", [user])
events = cur.fetchall()
# instantiate an instance of `SomeClass`
return data
So how would I create an instance of SomeClass and pass name and date entries to my newly created instance?

Since fetchall() returns a list of the rows, you should be able to do this (this should cover occasions where multiple results are returned as well):
for result in events:
my_instance = SomeClass(result[0], result[1])
# Do whatever you want to do with the instances, which looks like
# it may be appending to data
data.append(my_instance) # Or data.append(SomeClass(result[0], result[1]))
Can't test it right now, so apologies if it is way off :)