Server Side Programming Articles - Page 2575 of 2650

In python there is no built−in or normal function that acts as an object inspector. But we can use functions like type(), help(), dir(), vars() or modules like inspect are used to find the attributes, properties and methods of any object. Also we have other functions like id(), getattr(), hasattr(), globals(), locals(), callable() are useful in looking inside an object to know its attributes and methods. Here we will inspect the objects using some built−in functions. Before that we will create a simple python class and its objects, to refer throughout this article. Following is the syntax to defing ... Read More

To wrap existing C or C++ functionality in Python, there are number of options available, which are: Manual wrapping using PyMethodDef and Py_InitModule, SWIG, Pyrex, ctypes, SIP, Boost.Python, and pybind1. Using the SWIG Module Let’s take a C function and then tune it to python using SWIG. The SWIG stands for “Simple Wrapper Interface Generator”, and it is capable of wrapping C in a large variety of languages like python, PHP, TCL etc. Example Consider simple factorial function fact() in example.c file. /* File : example.c */ #include // calculate factorial int fact(int n) ... Read More

To encode custom python objects as BSON with Pymongo, you have to write a SONManipulator. From the docs:SONManipulator instances allow you to specify transformations to be applied automatically by PyMongo.from pymongo.son_manipulator import SONManipulator class Transform(SONManipulator):   def transform_incoming(self, son, collection):     for (key, value) in son.items():       if isinstance(value, Custom):         son[key] = encode_custom(value)       elif isinstance(value, dict): # Make sure we recurse into sub-docs         son[key] = self.transform_incoming(value, collection)     return son   def transform_outgoing(self, son, collection):     for (key, value) in son.items():       ... Read More

Python is an object-oriented programming language, here attributes are known as properties of an object. By using different methods, we can check if an object has an attribute or not. To check if an object contains a particular attribute then we can use hasattr() method and getattr() method. Or if we want to get all existing attributes then we can use the dir() method. (Learn more about Python directories: Python Directories Tutorial) Initially create a dummy Python class with two attributes then assign it to an object, and it will refer throughout this article. class DummyClass(): ... Read More

Assuming that a MySQL database named 'test' is present on the server and a table named employee is also created. Let the table have five fields fname, lname, age, gender, and salary.Suppose we want to insert a tuple object containing data of a record defined as follows into the Msql database.t1=('Steven', 'Assange', 21, 'M', 2001)To establish an interface between MySQL and Python 3, you need to install the PyMySQL module. Then you can set up the connection using the following statementsimport PyMySQL # Open database connection db = PyMySQL.connect("localhost", "root", "", "test" ) # prepare a cursor object using cursor() ... Read More

By using pymongo library, we can insert a Python object into MongoDB, which is a widely used MongoDB driver for Python. To insert a Python object represented as a dictionary, we have to establish the setup for a MongoDB client and connect to a database and collection. Before starting, ensure you have installed Python 3 (along with PIP) and MongoDB. The following are the steps for inserting a Python object in MongoDB. Install PyMongo ... Read More

We need sometimes to compress Python objects (list, dictionary, string, etc) before saving them to cache and decompress after reading from cache.Firstly we need to be sure we need to compress the objects. We should check if  the data structures/objects are too big just to fit uncompressed in the cache. There is going to be an overhead for compression/decompression, that we have to tradeoff with the gains made by caching in the first place.If we really need compression, then we probably want to use zlib.If we are going to use zlib, we might want to experiment with the different compression ... Read More

Here is an example in which a simple Python object is wrapped and embedded. We are using  .c for this, c++ has similar steps −class PyClass(object):     def __init__(self):         self.data = []     def add(self, val):         self.data.append(val)     def __str__(self):         return "Data: " + str(self.data) cdef public object createPyClass():     return PyClass() cdef public void addData(object p, int val):     p.add(val) cdef public char* printCls(object p):     return bytes(str(p), encoding = 'utf-8')We compile with cython pycls.pyx (use --cplus for c++) to generate ... Read More

The following code shows how to get return value from a function in a Python class.Exampleclass Score():     def __init__(self):         self.score = 0         self.num_enemies = 5         self.num_lives = 3     def setScore(self, num):         self.score = num     def getScore(self):          return self.score     def getEnemies(self):         return self.num_enemies     def getLives(self):         return self.num_lives         s = Score() s.setScore(9) print s.getScore() print s.getEnemies() print s.getLives()Output9 5 3

In Python, we can return an object from a function, using the return keyword, just like any other variable. The statements after the return will not be executed. The return keyword cannot be used outside the function. If the function has a return statement without any expression, then the special value None is returned. In the following example, the function returned the sum of two numbers - def Sum(a, b): return a+b my_var1 = 23 my_var2 = 105 result_1 = Sum(my_var1, my_var2) # function call print(result_1) Following is an output of ... Read More