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What's the difference between a proc and a lambda in Ruby?
...ept the resulting Proc objects check the number of parameters passed when called.
An example:
p = Proc.new {|a, b| puts a**2+b**2 } # => #<Proc:0x3c7d28@(irb):1>
p.call 1, 2 # => 5
p.call 1 # => NoMethodError: undefined method `**' for nil:NilClass
p.call 1, 2, 3 # => 5
l = lamb...
How to display all methods of an object?
I want to know how to list all methods available for an object like for example:
8 Answers
...
g++ undefined reference to typeinfo
...ill contain null-pointer most likely). However, nobody prohibits you from calling this pure virtual function in a non-virtual manner, i.e. by using a fully-qualified name. In this case the linker will look for the body, and you will have to define the function. And yes, you can define a body for a p...
Redirecting Output from within Batch file
... good and fast way that only opens and positions the file once
@echo off
call :sub >output.txt
exit /b
:sub
command1
command2
...
commandN
Edit 2020-04-17
Every now and then you may want to repeatedly write to two or more files. You might also want different messages on the screen. It is sti...
Is there a portable way to get the current username in Python?
... to combine os.getuid() with pwd.getpwuid():
import os
import pwd
def get_username():
return pwd.getpwuid( os.getuid() )[ 0 ]
Refer to the pwd docs for more details:
http://docs.python.org/library/pwd.html
share
...
How do I sort a dictionary by value?
...(x.items(), key=operator.itemgetter(0))
In Python3 since unpacking is not allowed [1] we can use
x = {1: 2, 3: 4, 4: 3, 2: 1, 0: 0}
sorted_x = sorted(x.items(), key=lambda kv: kv[1])
If you want the output as a dict, you can use collections.OrderedDict:
import collections
sorted_dict = collection...
Python CSV error: line contains NULL byte
..., but not cause any other dramas. I also note that you have several files (all opened with 'rU' ??) but only one causing a problem.
If the csv module says that you have a "NULL" (silly message, should be "NUL") byte in your file, then you need to check out what is in your file. I would suggest that...
WITH CHECK ADD CONSTRAINT followed by CHECK CONSTRAINT vs. ADD CONSTRAINT
...
It doesn't look like WITH CHECK is actually the default, it's only the default for new data. From msdn.microsoft.com/en-us/library/ms190273.aspx: "If not specified, WITH CHECK is assumed for new constraints, and WITH NOCHECK is assumed for re-enabled constraints."...
Find out whether Chrome console is open
... answer. This solution takes advantage of the fact that toString() is not called on logged objects unless the console is open.
var devtools = /./;
devtools.toString = function() {
if (!this.opened) {
alert("Opened");
}
this.opened = true;
}
console.log('%c', devtools);
// devtools.ope...
Node: log in a file instead of the console
...
Due to a recent change, you can't call stderr.pipe() anymore - it takes this now: process.__defineGetter__('stderr', function() { return fs.createWriteStream(__dirname + '/error.log', {flags:'a'}) })
– damianb
Feb 23 '13 ...