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Python Articles
Page 842 of 855
Python Utilities for with-statement contexts (contextlib)
contextlib module of Python's standard library defines ContextManager class whose object properly manages the resources within a program. Python has with keyword that works with context managers. The file object (which is returned by the built-in open() function) supports ContextManager API. Hence we often find with keyword used while working with files.Following code block opens a file and writes some data in it. After the operation is over, the file is closed, failing which file descriptor is likely to leak leading to file corruption.f = open("file.txt", "w") f.write("hello world") f.close()However same file operation is done using file's context manager capability ...
Read MoreTop-level script environment in Python (__main__)
A module object is characterized by various attributes. Attribute names are prefixed and post-fixed by double underscore __. The most important attribute of module is __name__. When Python is running as a top level executable code, i.e. when read from standard input, a script, or from an interactive prompt the __name__ attribute is set to '__main__'.>>> __name__ '__main__'From within a script also, we find a value of __name__ attribute is set to '__main__'. Execute the following script.'module docstring' print ('name of module:', __name__)Outputname of module: __main__However, for an imported module this attribute is set to name of the Python script. ...
Read MoreBuilt-in objects in Python (builtins)
The builtins module is automatically loaded every time Python interpreter starts, either as a top level execution environment or as interactive session. The Object class, which happens to be the base class for all Python objects, is defined in this module. All built-in data type classes such as numbers, string, list etc are defined in this module. The BaseException class, as well as all built-in exceptions, are also defined in it. Further, all built-in functions are also defined in the built-ins module.Since this module is imported in the current session automatically, normally it is not imported explicitly. All the built-in ...
Read MoreAccessing The Unix/Linux password database (pwd)
The pwd module in standard library of Python provides access to the password database of user accounts in a Unix/Linux operating system. Entries in this Password database are atored as a tuple-like object. The structure of tuple is according to following passwd structure pwd.h file in CPython APIIndexAttributeMeaning0pw_nameLogin name1pw_passwdOptional encrypted password2pw_uidNumerical user ID3pw_gidNumerical group ID4pw_gecosUser name or comment field5pw_dirUser home directory6pw_shellUser command interpreterThe pwd module defines the following functions −>>> import pwd >>> dir(pwd) ['__doc__', '__loader__', '__name__', '__package__', '__spec__', 'getpwall', 'getpwnam', 'getpwuid', 'struct_passwd']getpwnam() − This function returns record in the password database corresponding to the specified user name>>> pwd.getpwnam('root') pwd.struct_passwd(pw_name ...
Read MorePage Rank Algorithm and Implementation using Python
The PageRank algorithm is applicable in web pages. Web page is a directed graph, we know that the two components of Directed graphsare -nodes and connections. The pages are nodes and hyperlinks are the connections, the connection between two nodes.We can find out the importance of each page by the PageRank and it is accurate. The value of the PageRank is the probability will be between 0 and 1.The PageRank value of individual node in a graph depends on the PageRank value of all the nodes which connect to it and those nodes are cyclically connected to the nodes whose ...
Read MoreDifferent Methods to find Prime Number in Python
First we need to know what a prime number is.A prime number always a positive integer number and divisible by exactly 2 integers (1 and the number itself), 1 is not a prime number.Now we shall discuss some methods to find Prime Number.Method1Using For loopsExampledef primemethod1(number): # Initialize a list my_primes = [] for pr in range(2, number): isPrime = True for i in range(2, pr): if pr % i == 0: isPrime = False if isPrime: my_primes.append(pr) print(my_primes) primemethod1(50)Output[2, 3, 5, 7, 11, ...
Read MorePython program to check if a string is palindrome or not
Given a string, our task is to check weather this string is palindrome or not.AlgorithmStep1: Enter string as an input. Step2: Using string slicing we reverse the string and compare it back to the original string. Step3: Then display the result.Example codemy_string=input("Enter string:") if(my_string==my_string[::-1]): print("The string is a palindrome") else: print("The string isn't a palindrome")OutputEnter string:madam The string is a palindrome Enter string:python The string isn't a palindrome
Read MoreDeque in Python
The Deque is basically a generalization of stack and queue structure, where it is initialized from left to right. It uses the list object to create a deque.It provides O(1) time complexity for popping and appending.The Dequeis a standard library class, which is located in the collections module.To use it at first we need to import it the collections standard library module.import collectionsIn this section we will see some functions of the Deque classThe Appending functions on DequeThere are two different types of append. The append() method is used to add elements at the right end of the queue, and ...
Read MoreRead and write tar archive files using Python (tarfile)
The ‘tar’ utility was originally introduced for UNIX operating system. Its purpose is to collect multiple files in a single archive file often called tarball which makes it easy to distribute the files. Functions in tarfile module of Python’s standard library help in creating tar archives and extracting from the tarball as required. The archives can be constructed with gzip, bz2 and lzma compressions or without any compression at all.Main function defined in this module is main() using which writing to tar file or reading from it is accomplished.Open()This function returns a TarFile object corresponding to file name which is ...
Read MorePython getpass Module
There are two functions defined in getpass module of Python’s standard library. They are useful whenever a terminal based application needs to be executed only after validating user credentials.getpass()This function prompts the user to enter a password. By default the keys entered by user in the terminal are not echoed. Also the default prompt that appears on terminal is ‘password’ which can be customized by providing a string as parameter.In following example, Python prompt is invoked from Command prompt terminal on Windows. The password entered is not echoed in the terminal.C:\python36>python Python 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 17:00:18) [MSC v.1900 ...
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