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What is “:-!!” in C code?
...ld.
The macro is somewhat misnamed; it should be something more like BUILD_BUG_OR_ZERO, rather than ...ON_ZERO. (There have been occasional discussions about whether this is a confusing name.)
You should read the expression like this:
sizeof(struct { int: -!!(e); }))
(e): Compute expression e....
How do I execute inserts and updates in an Alembic upgrade script?
... other forms.
Note that Alembic provides some basic data functions: op.bulk_insert() and op.execute(). If the operations are fairly minimal, use those. If the migration requires relationships or other complex interactions, I prefer to use the full power of models and sessions as described below.
T...
pandas dataframe columns scaling with sklearn
...ndas dataframe with mixed type columns, and I'd like to apply sklearn's min_max_scaler to some of the columns. Ideally, I'd like to do these transformations in place, but haven't figured out a way to do that yet. I've written the following code that works:
...
How to convert An NSInteger to an int?
...endently of whether you are building for a 32-bit or a 64-bit system.
#if __LP64__ || TARGET_OS_EMBEDDED || TARGET_OS_IPHONE || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64
typedef long NSInteger;
#else
typedef int NSInteger;
#endif
You can use NSInteger any place you use an int without converting it....
How to convert CFStringRef to NSString?
...e using ARC, the new casting syntax is as follows:
NSString *aNSString = (__bridge NSString *)aCFString;
works as well. The key thing to note is that CoreFoundation will often return objects with +1 reference counts, meaning that they need to be released (all CF[Type]Create format functions do th...
Print current call stack from a method in Python code
...port traceback
def f():
g()
def g():
for line in traceback.format_stack():
print(line.strip())
f()
# Prints:
# File "so-stack.py", line 10, in <module>
# f()
# File "so-stack.py", line 4, in f
# g()
# File "so-stack.py", line 7, in g
# for line in traceback.form...
Is there a math nCr function in python? [duplicate]
...
def nCr(n,r):
f = math.factorial
return f(n) / f(r) / f(n-r)
if __name__ == '__main__':
print nCr(4,2)
In Python 3, use the integer division // instead of / to avoid overflows:
return f(n) // f(r) // f(n-r)
Output
6
...
MFC 获取当前时间的几种方法总结 - C/C++ - 清泛网 - 专注C/C++及内核技术
...ime curTime = CTime::GetCurrentTime();CString strCurTime;strCurTime.Format(_T("d d d d:d:d"), curTime...1.CTime类获取当前时间
CTime curTime = CTime::GetCurrentTime();
CString strCurTime;
strCurTime.Format(_T("d/d/d d:d:d"), curTime.GetYear(), curTime.GetMonth(), curTime.GetDay(), curTi...
Google breakpad stackwalker无法加载符号 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...Google breakpad安装好以后，按要求生成 sym，但是最终minidump_stackwalk打印出来的堆栈还是提示找不到符号。这是因为它要求符号文件有一 Google breakpad安装好以后，按要求生成.sym，但是最终 minidump_stackwalk 打印出来的堆栈还是提示...
Best way to select random rows PostgreSQL
...ery:
SELECT count(*) AS ct -- optional
, min(id) AS min_id
, max(id) AS max_id
, max(id) - min(id) AS id_span
FROM big;
The only possibly expensive part is the count(*) (for huge tables). Given above specifications, you don't need it. An estimate will do just fine,...