SimPy (rhymes with “Blimpie”) is a python package for process-oriented discrete-event simulation.InstallationThe easiest way to install SimPy is via pip:pip install simpyAnd the output you may get will be something like, At the time of writing, simpy-3.0.11 is the most recent version of SimPy, and we will use it for all the below examples.In case, SimPy is already installed, use the –U option for pip to upgrade.pip install –U simpyNote: You need to have python 2.7 or above version and for Linux/Unix/MacOS you may need root privileges to install SimPy.To check if SimPy was successfully installed, open a python shell ... Read More

The ModuleFinder class in 'modulefinder' module can determine set of modules imported by a certain script. This module has a command line interface as well as programmatic interface.For demonstration of functionality, use following script#modfinder.py import hello try: import trianglebrowser import nomodule, mymodule except ImportError: passCommand line interfaceFollowing command displays list of modules located as well as not found.E:\python37>python -m modulefinder modfinder.pyOutputName File ---- ---- m __main__ modfinder.py m hello hello.py m math m trianglebrowser trianglebrowser.py Missing modules: ? mymodule imported from __main__ ? nomodule imported from __main__Programmatic interfaceModuleFinder class in ... Read More

Automatic garbage collection is one of the important features of Python. Garbage collector mechanism attempts to reclaim memory occupied by objects that are no longer in use by the program.Python uses reference counting mechanism for garbage collection. Python interpreter keeps count of number of times an object is referenced by other objects. When references to an object are removed, the count for an object is decremented. When the reference count becomes zero, the object memory is reclaimed.Normally this mechanism is performed automatically. However, it can be done on purpose if a certain situation arises in the program. The 'gc' module ... Read More

Warning is different from error in a program. If error is encountered, Python program terminates instantly. Warning on the other hand is not fatal. It displays certain message but program continues. Warnings are issued to alert the user of certain conditions which aren't exactly exceptions. Typically warning appears if some deprecated usage of certain programming element like keyword/function/class etc. is found.Warning messages are displayed by warn() function defined in 'warning' module of Python's standard library. Warning is actually a subclass of Exception in built-in class hierarchy. There are a number of built-in Warning subclasses. User defined subclass can also be ... Read More

Provisions of the struct module in the Python library are useful in performing conversions between C type structs and Python bytes objects. This can be achieved by module level functions as well as Struct class and its methods as defined in the struct module.The conversion functions use a format string. The byte order, size, and alignment used in the format string is determined by formatting character as per the following tableCharacterByte orderSizeAlignment@nativenativenative=nativestandardnonebig-endianstandardnone!network (= big-endian)standardnoneFollowing table shows format characters used to denote C type variables and corresponding Python types.FormatC TypePython typexpad byteno valueccharbytes of length 1b/Bsigned/unsigned charinteger?_Boolboolh/Hshort/unsigned shortintegeri/Iint/unsigned intintegerl/Llong/unsigned longintegerffloatfloatddoublefloatschar[]bytespchar[]bytesPvoid *integerFollowing ... Read More

A class is called an Abstract class if it contains one or more abstract methods. An abstract method is a method that is declared, but contains no implementation. Abstract classes may not be instantiated, and its abstract methods must be implemented by its subclasses.Abstract base classes provide a way to define interfaces when other techniques like hasattr() would be clumsy or subtly wrong (for example with magic methods). ABCs introduce virtual subclasses, which are classes that don’t inherit from a class but are still recognized by isinstance() and issubclass() functions. There are many built-in ABCs in Python. ABCs for Data ... Read More

Use of 'zipimport' module makes it possible to import Python modules and packages from ZIP-format archives. This module also allows an item of sys.path to be a string naming a ZIP file archive. Any files may be present in the ZIP archive, but only files .py and .pyc are available for import. ZIP import of dynamic modules is disallowed.Functionality of this module is explained by first building a zip archive of files in 'newdir' directory. Following files are assumed to be present in newdir directory['guess.py', 'hello.py', 'impzip.py', 'mytest.py', 'prime.py', 'prog.py', 'tmp.py']import sys, glob import zipfile files = glob.glob("*.py") print (files) ... Read More

The pyclbr module in Python library extracts information about the functions, classes, and methods defined in a Python module. The information is extracted from the Python source code rather than by importing the module.This module defines readmodule() function that return a dictionary mapping module-level class names to class descriptors. The function takes a module name as parameter. It may be the name of a module within a package. In that case path is a sequence of directory paths prepended to sys.path, which is used to locate the module source code.Following code uses readmodule() function to parse classes and methods in ... Read More

Python is an interpreter based language. However it internally compiles the source code to byte code when a script (.py extension) is run and afterwards the bytecode version is automatically removed. When a module (apart from the precompiled built-in modules) is first imported, its compiled version is also automatically built but saved with .pyc extension in __pycache__ folder. Subsequent calls to import same module again won't recompile the module instead uses the one already built.However, a Python script file with .py extension can be compiled expilicitly without running it. The 'py_compile' module contains 'compile()' function for that purpose. Name of ... Read More

Function in the 'trace' module in Python library generates trace of program execution, and annotated statement coverage. It also has functions to list functions called during run by generating caller relationships.Following two Python scripts are used as an example to demonstrate features of trace module.#myfunctions.py import math def area(x): a = math.pi*math.pow(x, 2) return a def factorial(x): if x==1: return 1 else: return x*factorial(x-1)#mymain.py import myfunctions def main(): x = 5 print ('area=', myfunctions.area(x)) ... Read More