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What is the logic behind the “using” keyword in C++?
...related to templates. Warning: there may be typos due to copying over from PDF.
First let’s consider a toy example:
template <typename T>
class MyAlloc {/*...*/};
template <typename T, class A>
class MyVector {/*...*/};
template <typename T>
struct Vec {
typedef MyVector<T...
How to search for a string in text files?
...CESS_READ)
if s.find('blabla') != -1:
print('true')
NOTE: in python 3, mmaps behave like bytearray objects rather than strings, so the subsequence you look for with find() has to be a bytes object rather than a string as well, eg. s.find(b'blabla'):
#!/usr/bin/env python3
import mmap
...
What is the difference between loose coupling and tight coupling in the object oriented paradigm?
...'s easier to test and maintain.
You may find this paper by Martin Fowler (PDF) helpful.
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Selecting multiple columns in a pandas dataframe
...lumns) then you can do this instead:
df1 = df.iloc[:, 0:2] # Remember that Python does not slice inclusive of the ending index.
Additionally, you should familiarize yourself with the idea of a view into a Pandas object vs. a copy of that object. The first of the above methods will return a new copy...
Compiling with g++ using multiple cores
...ou run in many environments, this can change a lot) you may use ubiquitous Python function cpu_count():
https://docs.python.org/3/library/multiprocessing.html#multiprocessing.cpu_count
Like this:
make -j $(python3 -c 'import multiprocessing as mp; print(int(mp.cpu_count() * 1.5))')
If you're as...
How to activate an Anaconda environment
...would need to set the PATH for your environment (so that it gets the right Python from the environment and Scripts\ on Windows).
Imagine you have created an environment called py33 by using:
conda create -n py33 python=3.3 anaconda
Here the folders are created by default in Anaconda\envs, so you...
__getattr__ on a module
... a class in sys.modules at import time) should be no longer necessary.
In Python 3.7+, you just use the one obvious way. To customize attribute access on a module, define a __getattr__ function at the module level which should accept one argument (name of attribute), and return the computed value ...
Autoreload of modules in IPython [duplicate]
Is there a way to have IPython automatically reload all changed code? Either before each line is executed in the shell or failing that when it is specifically requested to. I'm doing a lot of exploratory programming using IPython and SciPy and it's quite a pain to have to manually reload each module...
Format a datetime into a string with milliseconds
...t;>>> OUTPUT >>>>
2020-05-04 10:18:32.926
Note: For Python3, print requires parentheses:
print(datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S.%f')[:-3])
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How do I convert seconds to hours, minutes and seconds?
...t into your desired output:
print('{:d}:{:02d}:{:02d}'.format(h, m, s)) # Python 3
print(f'{h:d}:{m:02d}:{s:02d}') # Python 3.6+
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