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How do pointer to pointers work in C?
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Let's assume an 8 bit computer with 8 bit addresses (and thus only 256 bytes of memory). This is part of that memory (the numbers at the top are the addresses):
54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69
+----+----+----+----+----+----+----+...
Read environment variables in Node.js
... Note that this will not be visible outside the node process and its subprocesses. E.g. it wouldn't be visible if you fire env in another shell window while the node process is running, nor in the same shell after the node process exits.
– Marko Bonaci
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Test if a variable is set in bash when using “set -o nounset”
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I tried this and I'm surprised this works... Everything is correct except according to "info bash", "${WHATEVER-}" should have a ":" (colon) before the "-" (dash) like: "${WHATEVER:-}", and "${WHATEVER+defined}" should have a colon before...
How to store a dataframe using Pandas
... it back using:
df = pd.read_pickle(file_name)
Note: before 0.11.1 save and load were the only way to do this (they are now deprecated in favor of to_pickle and read_pickle respectively).
Another popular choice is to use HDF5 (pytables) which offers very fast access times for large datasets:
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How to check whether a file or directory exists?
...(err) { return false, nil }
return false, err
}
Edited to add error handling.
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Cropping an UIImage
...a scaled chunk of the center of the image - I use this to take a UIImage and return a small, square representation of an image, similar to what's seen in the album view of the Photos app. (I know I could use a UIImageView and adjust the crop mode to achieve the same results, but these images are...
.NET: Simplest way to send POST with data and read response
...rol over the HTTP headers, you could attempt the same using HttpWebRequest and reference RFC2616 (w3.org/Protocols/rfc2616/rfc2616.txt). Answers from jball and BFree follow that attempt.
– Chris Hutchinson
Nov 3 '10 at 15:30
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What is the difference between ${var}, “$var”, and “${var}” in the Bash shell?
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Braces ($var vs. ${var})
In most cases, $var and ${var} are the same:
var=foo
echo $var
# foo
echo ${var}
# foo
The braces are only needed to resolve ambiguity in expressions:
var=foo
echo $varbar
# Prints nothing because there is no variable 'varbar'
echo ${var}bar...
What is the difference between `sorted(list)` vs `list.sort()`?
list.sort() sorts the list and replaces the original list, whereas sorted(list) returns a sorted copy of the list, without changing the original list.
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Why do people write the #!/usr/bin/env python shebang on the first line of a Python script?
...y having a #! at the start of the first line, followed by the interpreter (and any flags it may need).
If you're talking about other platforms, of course, this rule does not apply (but that "shebang line" does no harm, and will help if you ever copy that script to a platform with a Unix base, such ...