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What does “program to interfaces, not implementations” mean?
...t worried about implementation and the interface signature determines what all operations can be done. This can be used to change the behavior of a program at run-time. It also helps you to write far better programs from the maintenance point of view.
Here's a basic example for you.
public enum La...
Python Nose Import Error
...stem path. The following fixed this:
source myvirtualenv/activate
pip install nose
which nosetests
/home/me/myvirtualenv/bin/nosetests
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Python exit commands - why so many and when should each be used?
...s functionality was included to help people who do not know Python. After all, one of the most likely things a newbie will try to exit Python is typing in quit.
Nevertheless, quit should not be used in production code. This is because it only works if the site module is loaded. Instead, this fun...
Useful code which uses reduce()? [closed]
...found for it besides + and * were with and and or, but now we have any and all to replace those cases.
foldl and foldr do come up in Scheme a lot...
Here's some cute usages:
Flatten a list
Goal: turn [[1, 2, 3], [4, 5], [6, 7, 8]] into [1, 2, 3, 4, 5, 6, 7, 8].
reduce(list.__add__, [[1, 2, 3]...
Practical usage of setjmp and longjmp in C
...n me where exactly setjmp() and longjmp() functions can be used practically in embedded programming? I know that these are for error handling. But I'd like to know some use cases.
...
How to redirect to a 404 in Rails?
...ou want to show a 404 page, create a render_404 method (or not_found as I called it) in ApplicationController like this:
def not_found
raise ActionController::RoutingError.new('Not Found')
end
Rails also handles AbstractController::ActionNotFound, and ActiveRecord::RecordNotFound the same way....
Django: multiple models in one template using forms [closed]
...eparate project) OR creating a new Customer, then creating a Ticket and finally creating a Note assigned to the new ticket.
...
Remove duplicate elements from array in Ruby
...
array = array.uniq
uniq removes all duplicate elements and retains all unique elements in the array.
This is one of many beauties of the Ruby language.
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How to check if a python module exists without importing it
...ING
When trying to find a submodule, it will import the parent module (for all of the above methods)!
food/
|- __init__.py
|- eggs.py
## __init__.py
print("module food loaded")
## eggs.py
print("module eggs")
were you then to run
>>> import importlib
>>> spam_spec = importli...
Can you grab or delete between parentheses in vi/vim?
...isual mode, then you specify that you want to go 2 levels of parens up. Finally the a) selects "a block". After that you can use d or x to delete, etc.
If you don't want to include the outer parens, you can use "inner block" instead:
v2i)
See :help object-select for the complete list of related ...