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Python: most idiomatic way to convert None to empty string?
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If you actually want your function to behave like the str() built-in, but return an empty string when the argument is None, do this:
def xstr(s):
if s is None:
return ''
return str(s)
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Is there a bash command which counts files?
... bash:
ls -1q log* | wc -l
ls -1q will give you one line per file, even if they contain whitespace or special characters such as newlines.
The output is piped to wc -l, which counts the number of lines.
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Best way to iterate through a Perl array
...g. breadth-first searches): my @todo = $root; while (@todo) { my $node = shift; ...; push @todo, ...; ...; }
– ikegami
Feb 2 '15 at 14:40
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Comparing two dictionaries and checking how many (key, value) pairs are equal
I have two dictionaries, but for simplification, I will take these two:
26 Answers
26
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Wolfram's Rule 34 in XKCD [closed]
... 0 1
6: 1 1 0
7: 1 1 1
If you're evaluating a stage in a cellular automaton (CA) that follows rule 2, then whenever a three-bit string matches rule 2's configuration, the center bit becomes (or stays, in this case) true on the next iteration.
A CA...
Get characters after last / in url
...tr returns everything after that position.
As mentioned by redanimalwar if there is no slash this doesn't work correctly since strrpos returns false. Here's a more robust version:
$pos = strrpos($url, '/');
$id = $pos === false ? $url : substr($url, $pos + 1);
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Append value to empty vector in R?
...abits). ;-)
Note that vector <- c() isn't an empty vector; it's NULL. If you want an empty character vector, use vector <- character().
Pre-allocate the vector before looping
If you absolutely must use a for loop, you should pre-allocate the entire vector before the loop. This will be muc...
In Python, how does one catch warnings as if they were exceptions?
...arnings.simplefilter("always")
# Trigger a warning.
fxn()
# Verify some things
assert len(w) == 1
assert issubclass(w[-1].category, DeprecationWarning)
assert "deprecated" in str(w[-1].message)
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how do I initialize a float to its max/min value?
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@Yacoby, you might want to clarify that numeric_limits<float>::min() doesn't mean most negative value, it means smallest positive.
– MSN
Apr 21 '10 at 16:35
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What is the EAFP principle in Python?
...e assumes the existence of valid keys or attributes and catches exceptions if the assumption proves false. This clean and fast style is characterized by the presence of many try and except statements. The technique contrasts with the LBYL style common to many other languages such as C.
An example ...