大约有 43,200 项符合查询结果（耗时：0.0362秒） [XML]
Pandas count(distinct) equivalent
...()
Example:
In [2]: table
Out[2]:
CLIENTCODE YEARMONTH
0 1 201301
1 1 201301
2 2 201301
3 1 201302
4 2 201302
5 2 201302
6 3 201302
In [3]: table.groupby('YEARMONTH').CLIENTCODE.nunique()
Out[3...
Aren't Python strings immutable? Then why does a + “ ” + b work?
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185
First a pointed to the string "Dog". Then you changed the variable a to point at a new string...
How is “int* ptr = int()” value initialization not illegal?
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110
int() is a constant expression with a value of 0, so it's a valid way of producing a null poin...
How to select a single field for all documents in a MongoDB collection?
In my MongoDB, I have a student collection with 10 records having fields name and roll . One record of this collection is:
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二维码的生成细节及原理 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...说一下二维码一共有40个尺寸。官方叫版本Version。Version 1是21 x 21的矩阵，Version 2是 25 x 25的矩阵，Version 3是29的尺寸，每增加一个version，就会增加4的尺寸，公式是：(V-1)*4 + 21（V是版本号） 最高Version 40，(40-1)*4+21 = 177，所以最高...
How to concatenate two MP4 files using FFmpeg?
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21 Answers
21
Active
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Explicitly select items from a list or tuple
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154
list( myBigList[i] for i in [87, 342, 217, 998, 500] )
I compared the answers with python ...
Rotating and spacing axis labels in ggplot2
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1159
Change the last line to
q + theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust...
How to list the contents of a package using YUM?
...d into one example:
$ repoquery -l time
/usr/bin/time
/usr/share/doc/time-1.7
/usr/share/doc/time-1.7/COPYING
/usr/share/doc/time-1.7/NEWS
/usr/share/doc/time-1.7/README
/usr/share/info/time.info.gz
On at least one RH system, with rpm v4.8.0, yum v3.2.29, and repoquery v0.0.11, repoquery -l rpm p...