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How can I check if a file exists in Perl?
...mething exists at given path using the -e file-test operator.
print "$base_path exists!\n" if -e $base_path;
However, this test is probably broader than you intend. The code above will generate output if a plain file exists at that path, but it will also fire for a directory, a named pipe, a syml...
Creating an empty list in Python
...ny list, and if I append something else, e.g.
t = t.append(2)
I get the error "'NoneType' object has no attribute 'append'". If, however, I create the list by
t = list() # explicit instantiation
then it works fine.
sh...
How to read from stdin line by line in Node
...
This doesn't work for me (node v9.2.0, Windows). Error: EISDIR: illegal operation on a directory, fstat at tryStatSync (fs.js:534:13)`
– AlexChaffee
Dec 18 '17 at 22:47
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How to update Python?
...switching bit-versions, remove the other bit-version first.
UPDATES: 2016-05-16
Anaconda and MiniConda can be used with an existing Python installation by disabling the options to alter the Windows PATH and Registry. After extraction, create a symlink to conda in your bin or install conda from Py...
OpenShift rhc setup using multiple accounts
I have two accounts on Openshift platform. How can I setup my computer so that I can manage both of them with rhc ? I cannot find any relevant option in the command line arguments.
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How to get the error message from the error code returned by GetLastError()?
After a Windows API call, how can I get the last error message in a textual form?
11 Answers
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What is the difference between DSA and RSA?
.../web.archive.org/web/20140212143556/http://courses.cs.tamu.edu:80/pooch/665_spring2008/Australian-sec-2006/less19.html
RSA
RSA encryption and decryption are commutative
hence it may be used directly as a digital signature scheme
given an RSA scheme {(e,R), (d,p,q)}
to sign a message M, compute:
...
Function to clear the console in R and RStudio
I am wondering if there is a function to clear the console in R and, in particular, RStudio I am looking for a function that I can type into the console, and not a keyboard shortcut.
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Why is a round-trip conversion via a string not safe for a double?
... - Mul64 will be called
// at most twice during the conversion, so the error won't propagate
// to any of the 53 significant bits of the result
unsigned long long val = Mul32x32To64(a >> 32, b >> 32) +
(Mul32x32To64(a >> 32, b) >> 32) +
(Mul32x32To...
Python - write() versus writelines() and concatenated strings
...ou provide a list of strings, it will raise an exception (by the way, show errors to us!).
writelines(arg) expects an iterable as argument (an iterable object can be a tuple, a list, a string, or an iterator in the most general sense). Each item contained in the iterator is expected to be a string....