大约有 40,000 项符合查询结果（耗时：0.0477秒） [XML]
How does collections.defaultdict work?
...
Usually, a Python dictionary throws a KeyError if you try to get an item with a key that is not currently in the dictionary. The defaultdict in contrast will simply create any items that you try to access (provided of course th...
Can Python print a function definition?
...pile a regular expression pattern, returning a pattern object."
return _compile(pattern, flags)
This will work in the interactive prompt, but apparently only on objects that are imported (not objects defined within the interactive prompt). And of course it will only work if Python can find th...
Bash empty array expansion with `set -u`
...ad. Other patterns, such as ${arr[@]-} or ${arr[@]:0}, are not safe across all major versions of Bash.
As the table below shows, the only expansion that is reliable across all modern-ish Bash versions is ${arr[@]+"${arr[@]}"} (column +"). Of note, several other expansions fail in Bash 4.2, includin...
Use of *args and **kwargs [duplicate]
...u're not sure how many arguments might be passed to your function, i.e. it allows you pass an arbitrary number of arguments to your function. For example:
>>> def print_everything(*args):
for count, thing in enumerate(args):
... print( '{0}. {1}'.format(count, thing))
...
...
Where does Scala look for implicits?
...
Implicits in Scala refers to either a value that can be passed "automatically", so to speak, or a conversion from one type to another that is made automatically.
Implicit Conversion
Speaking very briefly about the latter type, if one calls a method m on an object o of a class C, and that class d...
What is in your Mathematica tool bag? [closed]
We all know that Mathematica is great, but it also often lacks critical functionality. What kind of external packages / tools / resources do you use with Mathematica?
...
How exactly does a generator comprehension work?
... generator expression is like a list comprehension, but instead of finding all the items you're interested and packing them into list, it waits, and yields each item out of the expression, one by one.
>>> my_list = [1, 3, 5, 9, 2, 6]
>>> filtered_list = [item for item in my_list i...
How to optimize for-comprehensions and loops in Scala?
...s Java. I'm revisiting some Project Euler problems in Scala that I originally tackled in Java. Specifically Problem 5: "What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?"
...
Dynamically set local variable [duplicate]
How do you dynamically set local variable in Python (where the variable name is dynamic)?
7 Answers
...
Getting MAC Address
... says that it will return a random long if it fails to detect the mac: "If all attempts to obtain the hardware address fail, we choose a random 48-bit number with its eighth bit set to 1 as recommended in RFC 4122." So check that eighth bit!
– deinonychusaur
Fe...