As of Python 3, the traceback is stored in the exception, so a simple raise e will do the (mostly) right thing: try: something() except SomeError as e: try: plan_B() except AlsoFailsError: raise e # or raise e from None – see below The traceback produced will include an additional notice that SomeError occurred while … Read more
Python’s complaining because the inner set objects are mutable and thus not hashable. The solution is to use frozenset for the inner sets, to indicate that you have no intention of modifying them.
You’re trying to access Outer’s class instance, from inner class instance. So just use factory-method to build Inner instance and pass Outer instance to it. class Outer(object): def createInner(self): return Outer.Inner(self) class Inner(object): def __init__(self, outer_instance): self.outer_instance = outer_instance self.outer_instance.somemethod() def inner_method(self): self.outer_instance.anothermethod()
Using list comprehension: >>> lst = [[‘a’,’b’,’c’], [1,2,3], [‘x’,’y’,’z’]] >>> lst2 = [item[0] for item in lst] >>> lst2 [‘a’, 1, ‘x’]
A nested dict is a dictionary within a dictionary. A very simple thing. >>> d = {} >>> d[‘dict1’] = {} >>> d[‘dict1’][‘innerkey’] = ‘value’ >>> d[‘dict1’][‘innerkey2’] = ‘value2’ >>> d {‘dict1’: {‘innerkey’: ‘value’, ‘innerkey2’: ‘value2’}} You can also use a defaultdict from the collections package to facilitate creating nested dictionaries. >>> import collections >>> … Read more
Use: from collections import defaultdict d = defaultdict(lambda: defaultdict(int)) This will create a new defaultdict(int) whenever a new key is accessed in d.
I know this is an old question, but HTML5 offers a couple new options. The first is to separate the form from the toolbar in the markup, add another form for the delete action, and associate the buttons in the toolbar with their respective forms using the form attribute. <form id=”saveForm” action=”/post/dispatch/save” method=”post”> <input type=”text” … Read more
While not strictly nested, you can use common table expressions to reuse previous queries in subsequent ones. To do this, the form of the statement you are looking for would be WITH x AS ( SELECT * FROM MyTable ), y AS ( SELECT * FROM x ) SELECT * FROM y
You could try some sort of COALESCE trick, eg: SELECT COALESCE( CASE WHEN condition1 THEN calculation1 ELSE NULL END, CASE WHEN condition2 THEN calculation2 ELSE NULL END, etc… )
Nested classes are cool for hiding implementation details. List: class List { public: List(): head(nullptr), tail(nullptr) {} private: class Node { public: int data; Node* next; Node* prev; }; private: Node* head; Node* tail; }; Here I don’t want to expose Node as other people may decide to use the class and that would hinder … Read more