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Using python's eval() vs. ast.literal_eval()?
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datamap = eval(raw_input('Provide some data here: ')) means that you actually evaluate the code before you deem it to be unsafe or not. It evaluates the code as soon as the function is called. See also the dangers of eval.
ast.literal_eval ra...
Get __name__ of calling function's module in Python
....stack()[1]
mod = inspect.getmodule(frm[0])
print '[%s] %s' % (mod.__name__, msg)
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Ignore python multiple return value
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One common convention is to use a "_" as a variable name for the elements of the tuple you wish to ignore. For instance:
def f():
return 1, 2, 3
_, _, x = f()
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Difference between Python's Generators and Iterators
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iterator is a more general concept: any object whose class has a __next__ method (next in Python 2) and an __iter__ method that does return self.
Every generator is an iterator, but not vice versa. A generator is built by calling a function that has one or more yield expressions (yield st...
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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Why exactly is eval evil?
...estion is not specific to LISP. Here is an answer on the same question for PHP, and it applies to LISP, Ruby, and other other language that has an eval:
The main problems with eval() are:
Potential unsafe input. Passing an untrusted parameter is a way to
fail. It is often not a trivial...
How to watch for array changes?
...ods or the length property).
function ObservableArray(items) {
var _self = this,
_array = [],
_handlers = {
itemadded: [],
itemremoved: [],
itemset: []
};
function defineIndexProperty(index) {
if (!(index in _self)) {
Object.defineProperty...
What is the most efficient way of finding all the factors of a number in Python?
...om functools import reduce
def factors(n):
return set(reduce(list.__add__,
([i, n//i] for i in range(1, int(n**0.5) + 1) if n % i == 0)))
This will return all of the factors, very quickly, of a number n.
Why square root as the upper limit?
sqrt(x) * sqrt(x) = x. So if t...
What does the “yield” keyword do?
...ou create the method of the node object that will return the generator
def _get_child_candidates(self, distance, min_dist, max_dist):
# Here is the code that will be called each time you use the generator object:
# If there is still a child of the node object on its left
# AND if the d...
Get exception description and stack trace which caused an exception, all as a string
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See the traceback module, specifically the format_exc() function. Here.
import traceback
try:
raise ValueError
except ValueError:
tb = traceback.format_exc()
else:
tb = "No error"
finally:
print tb
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