大约有 30,000 项符合查询结果（耗时：0.0988秒） [XML]
Python argparse mutual exclusive group
...
add_mutually_exclusive_group doesn't make an entire group mutually exclusive. It makes options within the group mutually exclusive.
What you're looking for is subcommands. Instead of prog [ -a xxxx | [-b yyy -c zzz]], you'd hav...
Is 'switch' faster than 'if'?
... your specific questions:
Clang generates one that looks like this:
test_switch(char): # @test_switch(char)
movl %edi, %eax
cmpl $19, %edi
jbe .LBB0_1
retq
.LBB0_1:
jmpq *.LJTI0_0(,%rax,8)
jmp void call<0u&g...
sqlalchemy: how to join several tables by one query?
...integer primary keys for everything, but whatever):
class User(Base):
__tablename__ = 'users'
email = Column(String, primary_key=True)
name = Column(String)
class Document(Base):
__tablename__ = "documents"
name = Column(String, primary_key=True)
author_email = Column(Strin...
Project structure for Google App Engine
... had trouble with packages. Just make sure each of your sub folders has an __init__.py file. It's ok if its empty.
Boilerplate files
These hardly vary between projects
app.yaml: direct all non-static requests to main.py
main.py: initialize app and send it all requests
Project lay-out
static...
When do you use map vs flatMap in RxJava?
...
answered Dec 9 '14 at 6:06
1vand1ng01vand1ng0
1,1231515 silver badges1717 bronze badges
...
How to print a dictionary line by line in Python?
...
I do print(json.dumps(cars, indent=4, ensure_ascii=False)) because otherwise non-ASCII characters are unreadable.
– Boris
Apr 22 at 16:36
add a ...
Does C++ support 'finally' blocks? (And what's this 'RAII' I keep hearing about?)
...ing a mutex:
// A class with implements RAII
class lock
{
mutex &m_;
public:
lock(mutex &m)
: m_(m)
{
m.acquire();
}
~lock()
{
m_.release();
}
};
// A class which uses 'mutex' and 'lock' objects
class foo
{
mutex mutex_; // mutex for l...
Which characters are valid in CSS class names/selectors?
...tly at the CSS grammar.
Basically1, a name must begin with an underscore (_), a hyphen (-), or a letter(a–z), followed by any number of hyphens, underscores, letters, or numbers. There is a catch: if the first character is a hyphen, the second character must2 be a letter or underscore, and the n...
Managing constructors with many parameters in Java
...er the following example
public class StudentBuilder
{
private String _name;
private int _age = 14; // this has a default
private String _motto = ""; // most students don't have one
public StudentBuilder() { }
public Student buildStudent()
{
return new Student...
How to write inline if statement for print?
... condition:
block
if expression (introduced in Python 2.5)
expression_if_true if condition else expression_if_false
And note, that both print a and b = a are statements. Only the a part is an expression. So if you write
print a if b else 0
it means
print (a if b else 0)
and similarly ...