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Summarizing multiple columns with dplyr? [duplicate]
...brary(dplyr)
library(purrrlyr)
library(data.table)
library(bench)
set.seed(123)
n <- 10000
df <- data.frame(
a = sample(1:5, n, replace = TRUE),
b = sample(1:5, n, replace = TRUE),
c = sample(1:5, n, replace = TRUE),
d = sample(1:5, n, replace = TRUE),
grp = sample(1:3, n, replac...
Python how to write to a binary file?
...FileBytes)
bytearray(b'{\x03\xff\x00d')
>>> bytes(newFileBytes)
'[123, 3, 255, 0, 100]'
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Does Python have “private” variables in classes?
...names the variable.
class A:
def __init__(self):
self.__var = 123
def printVar(self):
print self.__var
Now, if you try to access __var outside the class definition, it will fail:
>>>x = A()
>>>x.__var # this will return error: "A has no attribute __var...
Retrieving parameters from a URL
...
import urlparse
url = 'http://example.com/?q=abc&p=123'
par = urlparse.parse_qs(urlparse.urlparse(url).query)
print par['q'][0], par['p'][0]
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Disabled href tag
...
You can use:
<a href="/" onclick="return false;">123n</a>
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jQuery deferreds and promises - .then() vs .done()
...tion (x) { // Suppose promise returns "abc"
console.log(x);
return 123;
}).then(function (x){
console.log(x);
}).then(function (x){
console.log(x)
})
The following results will get logged:
abc
123
undefined
While
promise.done(function (x) { // Suppose promise returns "abc"
...
Write a number with two decimal places SQL server
...ters to display, and the number of decimal places to display
Select Str(12345.6789, 12, 3)
displays: ' 12345.679' ( 3 spaces, 5 digits 12345, a decimal point, and three decimal digits (679). - it rounds if it has to truncate, (unless the integer part is too large for the total size, in whic...
Why does Javascript's regex.exec() not always return the same value? [duplicate]
...ignment as the loop condition.
var re = /foo_(\d+)/g,
str = "text foo_123 more text foo_456 foo_789 end text",
match,
results = [];
while (match = re.exec(str))
results.push(+match[1]);
DEMO: http://jsfiddle.net/pPW8Y/
If you don't like the placement of the assignment, the loo...
linux svn搭建配置及svn命令详解 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...asswd
[users]
# harry = harryssecret
# sally = sallyssecret
hello=123
用户名=密码
这样我们就建立了hello用户， 123密码
2.2 再设置权限authz
[root@www ~]# vi authz
[/]
hello= rw
意思是hello用户对所有的目录有读写权限，当然也...
Map vs Object in JavaScript
...d Symbol keys where as Maps support more or less any key type.
If I do obj[123] = true and then Object.keys(obj) then I will get ["123"] rather than [123]. A Map would preserve the type of the key and return [123] which is great. Maps also allow you to use Objects as keys. Traditionally to do this y...