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How to add an empty column to a dataframe?
...p
>>> import pandas as pd
>>> df = pd.DataFrame({"A": [1,2,3], "B": [2,3,4]})
>>> df
A B
0 1 2
1 2 3
2 3 4
>>> df["C"] = ""
>>> df["D"] = np.nan
>>> df
A B C D
0 1 2 NaN
1 2 3 NaN
2 3 4 NaN
...
How do I compare two DateTime objects in PHP 5.2.8?
...
<?php
date_default_timezone_set('Europe/London');
$d1 = new DateTime('2008-08-03 14:52:10');
$d2 = new DateTime('2008-01-03 11:11:10');
var_dump($d1 == $d2);
var_dump($d1 > $d2);
var_dump($d1 < $d2);
?>
bool(false)
bool(true)
bool(false)
dev:~# php -v
PHP 5.2.6-1+lenny3 with Suhosin-Pa...
NTFS performance and large volumes of files and directories
...
274
Here's some advice from someone with an environment where we have folders containing tens of m...
Removing projects in Sublime Text 2 and 3
How do you remove a project from Sublime Text 2 and 3's project windows ( Ctrl + Alt + P ) ?
5 Answers
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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
...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，所以最高是...
How can I check which version of Angular I'm using?
...
28 Answers
28
Active
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String's Maximum length in Java - calling length() method
... that would be returned by the method would be Integer.MAX_VALUE, which is 2^31 - 1 (or approximately 2 billion.)
In terms of lengths and indexing of arrays, (such as char[], which is probably the way the internal data representation is implemented for Strings), Chapter 10: Arrays of The Java Langu...
Oracle JDBC ojdbc6 Jar as a Maven Dependency
...>
<artifactId>ojdbc6</artifactId>
<version>11.2.0.3</version>
</dependency>
...
<repositories>
<repository>
<id>codelds</id>
<url>https://code.lds.org/nexus/content/groups/main-repo</url>
</repositor...
Pandas groupby: How to get a union of strings
...s+')
In [5]: df
Out[5]:
A B C
0 1 0.749065 This
1 2 0.301084 is
2 3 0.463468 a
3 4 0.643961 random
4 1 0.866521 string
5 2 0.120737 !
In [6]: df.dtypes
Out[6]:
A int64
B float64
C object
dtype: object
When you apply your own functi...
How to shift a column in Pandas DataFrame
...
In [18]: a
Out[18]:
x1 x2
0 0 5
1 1 6
2 2 7
3 3 8
4 4 9
In [19]: a.x2 = a.x2.shift(1)
In [20]: a
Out[20]:
x1 x2
0 0 NaN
1 1 5
2 2 6
3 3 7
4 4 8
...