大约有 44,000 项符合查询结果（耗时：0.0373秒） [XML]
Adding :default => true to boolean in existing Rails column
...dding a default boolean value to an existing column. So I tried the change_column suggestion but I mustn't be doing it right.
...
Java regex email
...ddresses. The Regexp's are very similar:
public static final Pattern VALID_EMAIL_ADDRESS_REGEX =
Pattern.compile("^[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,6}$", Pattern.CASE_INSENSITIVE);
public static boolean validate(String emailStr) {
Matcher matcher = VALID_EMAIL_ADDRESS_REGEX.matche...
What's the difference between assignment operator and copy constructor?
...tialized object from some other object's data.
A(const A& rhs) : data_(rhs.data_) {}
For example:
A aa;
A a = aa; //copy constructor
An assignment operator is used to replace the data of a previously initialized object with some other object's data.
A& operator=(const A& rhs) {...
How to get all subsets of a set? (powerset)
...3,) (1,2) (1,3) (2,3) (1,2,3)"
s = list(iterable)
return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
Output:
>>> list(powerset("abcd"))
[(), ('a',), ('b',), ('c',), ('d',), ('a', 'b'), ('a', 'c'), ('a', 'd'), ('b', 'c'), ('b', 'd'), ('c', 'd'), ('a', 'b', 'c'...
clear javascript console in Google Chrome
...
Chrome:
console._commandLineAPI.clear();
Safari:
console._inspectorCommandLineAPI.clear();
You can create your own variable, which works in both:
if (typeof console._commandLineAPI !== 'undefined') {
console.API = console._commandL...
Calling async method synchronously
...SynchronizationContext.Post serializes async continuations: Task newTask = _lastScheduledTask.ContinueWith(_ => SafeWrapCallback(action)); _lastScheduledTask = newTask;
– noseratio
Aug 26 '15 at 23:36
...
get path for my .exe [duplicate]
...
in visualstudio 2008 you could use this code :
var _assembly = System.Reflection.Assembly
.GetExecutingAssembly().GetName().CodeBase;
var _path = System.IO.Path.GetDirectoryName(_assembly) ;
...
how to clear the screen in python [duplicate]
... To avoid the 0 (system's return value) being shown, use absolutely_unused_variable = os.system("cls") or absolutely_unused_variable = os.system("clear")
– Shiva
Jul 4 '15 at 8:01
...
How to convert a PIL Image into a numpy array?
....readthedocs.io/en/3.4.x/reference/…), but a pillow image implements the __array_interface__ which numpy can use to access the raw bytes of an image without having to pass through an iterator (see github.com/python-pillow/Pillow/blob/… and docs.scipy.org/doc/numpy/reference/arrays.interface.html...
Numpy: find first index of value fast
...The code will be compiled so it will be fast.
@jit(nopython=True)
def find_first(item, vec):
"""return the index of the first occurence of item in vec"""
for i in xrange(len(vec)):
if item == vec[i]:
return i
return -1
and then:
>>> a = array([1,7,8,32])
...