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if A vs if A is not None:
...f object() is not None: pass is ~0.135 usec. Anyway, you should not use performance to choose between these two, but rather look at the differences in how they work, since they are not equivalent.
– Lauritz V. Thaulow
Oct 19 '11 at 8:02
...
Extract traceback info from an exception object
...es are minimally described as part of the raise documentation.
All credit for this part of the answer should go to Vyctor, who first posted this information. I'm including it here only because this answer is stuck at the top, and Python 3 is becoming more common.
In Python 2
It's annoyingly compl...
How to pretty print nested dictionaries?
...
I'm not sure how exactly you want the formatting to look like, but you could start with a function like this:
def pretty(d, indent=0):
for key, value in d.items():
print('\t' * indent + str(key))
if isinstance(value, dict):
pretty(value, ...
What does extern inline do?
...ll not generate an out-of-line version, but might call one (which you therefore must define in some other compilation unit. The one-definition rule applies, though; the out-of-line version must have the same code as the inline offered here, in case the compiler calls that instead.
static inline will...
What does if __name__ == “__main__”: do?
... following is in a file called foo.py.
# Suppose this is foo.py.
print("before import")
import math
print("before functionA")
def functionA():
print("Function A")
print("before functionB")
def functionB():
print("Function B {}".format(math.sqrt(100)))
print("before __name__ guard")
if __...
Django dynamic model fields
...define their own data fields (via the admin) to collect additional data in forms and report on the data. The latter bit makes JSONField not a great option, so instead I have the following solution:
...
After Installing Java JDK 7 For Mac OS X - mvn -version still shows java version 1.6.0_31
Oracle released Java JDK 7 on April 26 for Mac OS X. I followed the install instructions and when I do java -version in a terminal window I get:
...
How can I read SMS messages from the device programmatically in Android?
...he result to prevent exception
do {
String msgData = "";
for(int idx=0;idx<cursor.getColumnCount();idx++)
{
msgData += " " + cursor.getColumnName(idx) + ":" + cursor.getString(idx);
}
// use msgData
} while (cursor.moveToNext());
} else {
/...
Callback functions in C++
...ctions of the standard algorithms library <algorithm> use callbacks. For example the for_each algorithm applies an unary callback to every item in a range of iterators:
template<class InputIt, class UnaryFunction>
UnaryFunction for_each(InputIt first, InputIt last, UnaryFunction f)
{
...
How to implement a good __hash__ function in python [duplicate]
...
__hash__ should return the same value for objects that are equal. It also shouldn't change over the lifetime of the object; generally you only implement it for immutable objects.
A trivial implementation would be to just return 0. This is always correct, but per...