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Delete column from pandas DataFrame
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As you've guessed, the right syntax is
del df['column_name']
It's difficult to make del df.column_name work simply as the result of syntactic limitations in Python. del df[name] gets translated to df.__delitem__(name) under the covers by Python.
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Best way to do multiple constructors in PHP
You can't put two __construct functions with unique argument signatures in a PHP class. I'd like to do this:
21 Answers
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Difference between exit() and sys.exit() in Python
...raising SystemExit. sys.exit does so in sysmodule.c:
static PyObject *
sys_exit(PyObject *self, PyObject *args)
{
PyObject *exit_code = 0;
if (!PyArg_UnpackTuple(args, "exit", 0, 1, &exit_code))
return NULL;
/* Raise SystemExit so callers may catch it or clean up. */
PyE...
error C2664: “std::list::list(const std::allocator &)”: 不能将参数 1...
...转换为“const std::allocator &”错误日志：error C2664: std::list<_Ty>::list(const std::allocator<_Ty> &): 不能将参数 1 从std::vector<_Ty>转换为const std::...错误日志：
error C2664: “std::list<_Ty>::list(const std::allocator<_Ty> &)”: 不能将参数 1 从
“std::vect...
How are Python's Built In Dictionaries Implemented?
...keys' hashes. You can think of it like this:
hash key dict_0 dict_1 dict_2...
...010001 ffeb678c 633241c4 fffad420 ...
... ... ... ... ...
For a 64 bit machine, this could save up to 16 bytes per key per extra dictionary.
Shared Keys for...
How to remove illegal characters from path and filenames?
...blic string ReplaceInvalidChars(string filename)
{
return string.Join("_", filename.Split(Path.GetInvalidFileNameChars()));
}
This answer was on another thread by Ceres, I really like it neat and simple.
share
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How to make my custom type to work with “range-based for loops”?
...C++ standard, is specified to expand to something equivalent to:
for( range_declaration : range_expression )
becomes:
{
auto && __range = range_expression ;
for (auto __begin = begin_expr,
__end = end_expr;
__begin != __end; ++__begin) {
range_declaration = *...
Representing graphs (data structure) in Python
... both ways). We'll handle that by adding a directed parameter to the Graph.__init__ method. We'll also add some other helpful methods.
import pprint
from collections import defaultdict
class Graph(object):
""" Graph data structure, undirected by default. """
def __init__(self, connection...
Behaviour of increment and decrement operators in Python
...so far as they don't explain what happens.
To be exact, +x evaluates to x.__pos__() and ++x to x.__pos__().__pos__().
I could imagine a VERY weird class structure (Children, don't do this at home!) like this:
class ValueKeeper(object):
def __init__(self, value): self.value = value
def __s...
error LNK2019: unresolved external symbol _WinMain@16 referenced in function ___tmainCRTStartup
...you can just hint at what your entry point is, because you haven't defined ___tmainCRTStartup. You can do this by adding the following to Properties -> Linker -> Command line:
/ENTRY:"mainCRTStartup"
This way you get rid of the console window.
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