大约有 7,000 项符合查询结果（耗时：0.0173秒） [XML]
Primary key or Unique index?
...lues in that column in two different rows. Example:
CREATE TABLE table1 (foo int, bar int);
CREATE UNIQUE INDEX ux_table1_foo ON table1(foo); -- Create unique index on foo.
INSERT INTO table1 (foo, bar) VALUES (1, 2); -- OK
INSERT INTO table1 (foo, bar) VALUES (2, 2); -- OK
INSERT INTO table1 (f...
Does python have an equivalent to Java Class.forName()?
... only refer to the top level module,
For example, if your class lives in foo.baz module, then m will be the module foo
We can easily obtain a reference to foo.baz using getattr( m, 'baz' )
To get from the top level module to the class, have to recursively use gettatr on the parts of the class nam...
Passing variables in remote ssh command
...ariables.
# The first one even contains whitespace and a newline.
readonly FOO=$'apjlljs ailsi \n ajlls\t éjij'
readonly BAR=ygnàgyààynygbjrbjrb
# Make a list of what you want to pass through SSH.
# (The “unset” is just in case someone exported
# an associative array with this name.)
unset ...
Dynamic constant assignment
...ject itself is different each time the method is called. For example:
def foo
p "bar".object_id
end
foo #=> 15779172
foo #=> 15779112
Perhaps if you explained your use case—why you want to change the value of a constant in a method—we could help you with a better implementation.
Per...
Operation on every pair of element in a list
...
my_list = [1,2,3,4]
for pair in itertools.product(my_list, repeat=2):
foo(*pair)
This is equivalent to:
my_list = [1,2,3,4]
for x in my_list:
for y in my_list:
foo(x, y)
Edit: There are two very similar functions as well, permutations() and combinations(). To illustrate how th...
Convert a string to regular expression ruby
...
"/[\w\s]+/".to_regexp => /[\w\s]+/
You also can use the modifier:
'/foo/i'.to_regexp => /foo/i
Finally, you can be more lazy using :detect
'foo'.to_regexp(detect: true) #=> /foo/
'foo\b'.to_regexp(detect: true) #=> %r{foo\\b}
'/foo\b/'.to_regexp(detect: true) #=> %r{f...
What is this weird colon-member (“ : ”) syntax in the constructor?
...tax (ala: new String("Name")). It fits in with the constructor better than Foo(int num) : m_Count = 5. Not to mention that classes must be constructed at this point anyway, since it's initialized here. Foo(int num) : Bar = num, wouldn't compile right. It just seems weird seeing Foo(int num) : m_Coun...
Mixins vs. Traits
...s (MA and MB) or traits (TA and TB) define method with the same definition foo():void.
Mixin MA {
foo():void {
print 'hello'
}
}
Mixin MB {
foo():void {
print 'bye'
}
}
Trait TA {
foo():void {
print 'hello'
}
}
Trait TB {
foo():void {
p...
Convert Go map to json
...arshal(datas)
fmt.Println(err)
// [] json: unsupported type: map[int]main.Foo
The thing is you cannot use integers as keys in JSON; it is forbidden. Instead, you can convert these values to strings beforehand, for instance using strconv.Itoa.
See this post for more details: https://stackoverflow...
mkdir -p functionality in Python [duplicate]
... What about distutils.dir_util.mkpath? It's pretty simple as mkpath('./foo/bar')
– auraham
Jan 15 '13 at 21:41
...