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“ValueError: zero length field name in format” error in Python 3.0,3.1,3.2
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I'm gonna guess that you are running python 2.6 by accident somehow.
This feature is only available for at least 3.1 if you are using python 3, or 2.7 if you are using python 2.
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Returning value from called function in a shell script
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282
A Bash function can't return a string directly like you want it to. You can do three things:
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Pandas dataframe get first row of each group
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248
>>> df.groupby('id').first()
value
id
1 first
2 first
3 first
4...
Set selected option of select box
...code into a $(document).ready:
$(function() {
$("#gate").val('gateway_2');
});
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Rotating videos with FFmpeg
... pass:
0 = 90CounterCLockwise and Vertical Flip (default)
1 = 90Clockwise
2 = 90CounterClockwise
3 = 90Clockwise and Vertical Flip
Use -vf "transpose=2,transpose=2" for 180 degrees.
Make sure you use a recent ffmpeg version from here (a static build will work fine).
Note that this will re-encod...
How can I obtain an 'unbalanced' grid of ggplots?
..., arrangeGrob(p,p,p, heights=c(3/4, 1/4, 1/4), ncol=1),
ncol=2)
Edit (07/2015): with v>2.0.0 you can use the layout_matrix argument,
grid.arrange(p,p,p,p, layout_matrix = cbind(c(1,1,1), c(2,3,4)))
shar...
How do I use spaces in the Command Prompt?
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267
Single quotation marks won't do in that case. You have to add quotation marks around each path...
MongoDB logging all queries
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268
You can log all queries:
$ mongo
MongoDB shell version: 2.4.9
connecting to: test
> use my...
How does Python 2 compare string and int? Why do lists compare as greater than numbers, and tuples g
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2 Answers
2
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How do you know when to use fold-left and when to use fold-right?
...re, you use a left fold. Example (haskell-style pseudocode)
foldl (-) [1, 2, 3] == (1 - 2) - 3 == 1 - 2 - 3 // - is left-associative
If your operator is right-associative (right fold), the parentheses would be set like this:
A x (B x (C x D))
Example: Cons-Operator
foldr (:) [] [1, 2, 3] == 1...