I use eval() and exec() function in recent python development, and i am not sure which function to use in which scenario, so i investigate python’s document and write down how to use them and the difference between eval() and exec() python function.

In Python, the __new__ method is similar to the __init__ method, but if both exist, the method __new__ executes first. In the base class Object, __new__ is defined as a static method and needs to pass a parameter cls.  The parameter cls represents the class that needs to be instantiated, and this parameter is provided

1. Get Current Time. >>> import datetime,time >>> >>> now = time.strftime(“%Y-%m-%d %H:%M:%S”) >>> >>> print(now) 2019-03-29 21:27:20 >>> >>> now = datetime.datetime.now() >>> >>> print(now) 2019-03-29 21:27:20.218849 2. Get The Date Of  Last Month’s Last Day. >>> delta_day = datetime.timedelta(1) >>> >>> this_month_first_day = datetime.date(datetime.date.today().year,datetime.date.today().month,1) >>> >>> this_month_first_day datetime.date(2019, 3, 1) >>> >>> last

Using url tag and reverse() function, you can avoid hard-coding urls in template html files and views. So that even if the url path changes, it has no effect on templates and views source code. In fact, in the template view, if you want to get the currently accessed url, it’s more convenient to use

There are three functions in Python to remove one string’s head and tail characters and the blank characters, they are strip, lstrip and rstrip. strip : Used to remove both head and tail characters and blank characters (includes \n, \r, \t,’   ‘). lstrip : Used to remove head characters and blank characters (includes \n,

The default Python version under CentOS is 2.6 or 2.7, and now more and more modules support Python 3, so it is very necessary to install a Python 3 in CentOS. Instead of upgrading Python 2 to Python 3, we’re talking about installation, where Python 2 and Python 3 coexist. If you want to upgrade