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How to check whether a pandas DataFrame is empty?
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505
You can use the attribute df.empty to check whether it's empty or not:
if df.empty:
print(...
SQL keys, MUL vs PRI vs UNI
...at column.
– pgoetz
Aug 7 '19 at 16:07
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What does the constant 0.0039215689 represent?
...
0.0039215689 is approximately equal to 1/255.
Seeing that this is OpenGL, performance is probably important. So it's probably safe to guess that this was done for performance reasons.
Multiplying by the reciprocal is faster...
Putting text in top left corner of matplotlib plot
...t is in data coords,
alternatively, you can specify text in axis coords (0,0 is lower-left
and 1,1 is upper-right). The example below places text in the center
of the axes::
text(0.5, 0.5,'matplotlib',
horizontalalignment='center',
verticalalignment='center',
transform = ax.t...
What is an IndexOutOfRangeException / ArgumentOutOfRangeException and how do I fix it?
...declared as:
byte[] array = new byte[4];
You can access this array from 0 to 3, values outside this range will cause IndexOutOfRangeException to be thrown. Remember this when you create and access an array.
Array Length
In C#, usually, arrays are 0-based. It means that first element has index 0...
Memcached下一站：HandlerSocket！ - 更多技术 - 清泛网 - 专注C/C++及内核技术
...期的数据，就会造成数据不一致。这在强调即时性的Web2.0时代，不可取。
Memcached崩溃后的雪崩效应：作为缓存的Memcached一旦崩溃，MySQL很可能在短时间内承受高负载而宕机。据说前段时间新浪微博就遭遇了这样的问题。
注：...
How can I perform a culture-sensitive “starts-with” operation from the middle of a string?
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+100
I'll consider the problem of many<->one/many casemappings first and separately from handling different Normalization forms.
Fo...
Tools for analyzing performance of a Haskell program
...oblem.
Run your program with +RTS -s
$ time ./A +RTS -s
./A +RTS -s
749700
9,961,432,992 bytes allocated in the heap
2,463,072 bytes copied during GC
29,200 bytes maximum residency (1 sample(s))
187,336 bytes maximum slop
**2 MB** total memory in use (0...
Index all *except* one item in python
.... For example, to make b a copy of a without the 3rd element:
a = range(10)[::-1] # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
b = [x for i,x in enumerate(a) if i!=3] # [9, 8, 7, 5, 4, 3, 2, 1, 0]
This is very general, and can be used with all iterables, including numpy arrays. If y...
Best way to combine two or more byte arrays in C#
...he suggested methods in a loop executed 1 million times using 3 arrays of 10 bytes each. Here are the results:
New Byte Array using System.Array.Copy - 0.2187556 seconds
New Byte Array using System.Buffer.BlockCopy - 0.1406286 seconds
IEnumerable<byte> using C# yield operator - 0....