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what is faster: in_array or isset? [closed]
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119
The answers so far are spot-on. Using isset in this case is faster because
It uses an O(1) h...
R programming: How do I get Euler's number?
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150
The R expression
exp(1)
represents e, and
exp(2)
represents e^2.
This works because exp...
Is there a way to pass optional parameters to a function?
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115
The Python 2 documentation, 7.6. Function definitions gives you a couple of ways to detect whe...
Python's json module, converts int dictionary keys to strings
... for the given language, are strings (or "scalars" in Perl). In perl $foo{1}, $foo{1.0}, and $foo{"1"} are all references to the same mapping in %foo --- the key is evaluated as a scalar!
JSON started as a Javascript serialization technology. (JSON stands for JavaScript Object Notation.) Naturall...
Concatenate two slices in Go
I'm trying to combine the slice [1, 2] and the slice [3, 4] . How can I do this in Go?
7 Answers
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How can I get the diff between all the commits that occurred between two dates with Git?
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11 Answers
11
Active
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Pandas aggregate count distinct
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153
How about either of:
>>> df
date duration user_id
0 2013-04-01 30 ...
Updating MySQL primary key
...update the primary key.
alter table xx drop primary key, add primary key(k1, k2, k3);
To fix things:
create table fixit (user_2, user_1, type, timestamp, n, primary key( user_2, user_1, type) );
lock table fixit write, user_interactions u write, user_interactions write;
insert into fixit
selec...
Paperclip::Errors::MissingRequiredValidatorError with Rails 4
...line to your Post model, after specifying has_attached_file :image
Option 1: Validate content type
validates_attachment_content_type :image, :content_type => ["image/jpg", "image/jpeg", "image/png", "image/gif"]
-OR- another way
validates_attachment :image, content_type: { content_type: ["im...