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Lua简明教程 - 脚本技术 - 清泛IT论坛，有思想、有深度
...ble来管理全局变量的，Lua把这些全局变量放在了一个叫“_G”的Table里。我们可以用如下的方式来访问一个全局变量（假设我们这个全局变量名叫globalVar）：_G.globalVar
_G["globalVar"]复制代码
我们可以通过下面的方式来遍历...
Is arr.__len__() the preferred way to get the length of an array in Python?
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my_list = [1,2,3,4,5]
len(my_list)
# 5
The same works for tuples:
my_tuple = (1,2,3,4,5)
len(my_tuple)
# 5
And strings, which are really just arrays of characters:
my_string = 'hello world'
len(my_string)
# 11
It was in...
Inverse dictionary lookup in Python
...s slow as yours, because it creates a list from the dict twice.
key = dict_obj.keys()[dict_obj.values().index(value)]
Or if you prefer brevity over readability you can save one more character with
key = list(dict_obj)[dict_obj.values().index(value)]
And if you prefer efficiency, @PaulMcGuire's...
Does Python have a string 'contains' substring method?
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Under the hood, Python will use __contains__(self, item), __iter__(self), and __getitem__(self, key) in that order to determine whether an item lies in a given contains. Implement at least one of those methods to make in available to your custom type.
...
os.path.dirname(__file__) returns empty
...get the dirname of the absolute path, use
os.path.dirname(os.path.abspath(__file__))
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Run function from the command line
...() somewhere below the function and it will execute when you do python your_file.py
For a neater solution you can use this:
if __name__ == '__main__':
hello()
That way the function will only be executed if you run the file, not when you import the file.
...
#define macro for debug printing in C?
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If you use a C99 or later compiler
#define debug_print(fmt, ...) \
do { if (DEBUG) fprintf(stderr, fmt, __VA_ARGS__); } while (0)
It assumes you are using C99 (the variable argument list notation is not supported in earlier versions). The do { ... } while (0...
Multiple variables in a 'with' statement?
...Unlike the contextlib.nested, this guarantees that a and b will have their __exit__()'s called even if C() or it's __enter__() method raises an exception.
You can also use earlier variables in later definitions (h/t Ahmad below):
with A() as a, B(a) as b, C(a, b) as c:
doSomething(a, c)
...
Are PHP include paths relative to the file or the calling code?
...f you want to make it matter, and do an include relative to B.php, use the __FILE__ constant (or __DIR__ since PHP 5.2 IIRC) which will always point to the literal current file that the line of code is located in.
include(dirname(__FILE__)."/C.PHP");
...
Understanding the main method of python [duplicate]
...is almost unique to the language(*).
The semantics are a bit subtle. The __name__ identifier is bound to the name of any module as it's being imported. However, when a file is being executed then __name__ is set to "__main__" (the literal string: __main__).
This is almost always used to separate...