Try hasattr(): if hasattr(a, ‘property’): a.property See zweiterlinde’s answer below, who offers good advice about asking forgiveness! A very pythonic approach! The general practice in python is that, if the property is likely to be there most of the time, simply call it and either let the exception propagate, or trap it with a try/except … Read more
Usually, activating a virtualenv gives you a shell function named: $ deactivate which puts things back to normal. I have just looked specifically again at the code for virtualenvwrapper, and, yes, it too supports deactivate as the way to escape from all virtualenvs. If you are trying to leave an Anaconda environment, the command depends … Read more
Given a module foo with method bar: import foo bar = getattr(foo, ‘bar’) result = bar() getattr can similarly be used on class instance bound methods, module-level methods, class methods… the list goes on.
In Python 3, you can use the sep= and end= parameters of the print function: To not add a newline to the end of the string: print(‘.’, end=”) To not add a space between all the function arguments you want to print: print(‘a’, ‘b’, ‘c’, sep=”) You can pass any string to either parameter, and … Read more
Variables declared inside the class definition, but not inside a method are class or static variables: >>> class MyClass: … i = 3 … >>> MyClass.i 3 As @millerdev points out, this creates a class-level i variable, but this is distinct from any instance-level i variable, so you could have >>> m = MyClass() >>> … Read more
Use str.lower(): “Kilometer”.lower()
>>> x = “Hello World!” >>> x[2:] ‘llo World!’ >>> x[:2] ‘He’ >>> x[:-2] ‘Hello Worl’ >>> x[-2:] ‘d!’ >>> x[2:-2] ‘llo Worl’ Python calls this concept “slicing” and it works on more than just strings. Take a look here for a comprehensive introduction.
The sorted() function takes a key= parameter newlist = sorted(list_to_be_sorted, key=lambda d: d[‘name’]) Alternatively, you can use operator.itemgetter instead of defining the function yourself from operator import itemgetter newlist = sorted(list_to_be_sorted, key=itemgetter(‘name’)) For completeness, add reverse=True to sort in descending order newlist = sorted(list_to_be_sorted, key=itemgetter(‘name’), reverse=True)
There isn’t a built-in flag yet, but you can use: pip list –outdated –format=freeze | grep -v ‘^\-e’ | cut -d = -f 1 | xargs -n1 pip install -U For older versions of pip: pip freeze –local | grep -v ‘^\-e’ | cut -d = -f 1 | xargs -n1 pip install -U The … Read more
some_list[-1] is the shortest and most Pythonic. In fact, you can do much more with this syntax. The some_list[-n] syntax gets the nth-to-last element. So some_list[-1] gets the last element, some_list[-2] gets the second to last, etc, all the way down to some_list[-len(some_list)], which gives you the first element. You can also set list elements … Read more