Use `&quot;\n&quot;` instead of `&#39;\n&#39;`

You can do this all in the File.open block:

    Dir.chdir &#39;C:/Users/name/Music&#39;
    music = Dir[&#39;C:/Users/name/Music/*.{mp3, MP3}&#39;]
    puts &#39;what would you like to call the playlist?&#39;
    playlist_name = gets.chomp + &#39;.m3u&#39;
    
    File.open playlist_name, &#39;w&#39; do |f|
      music.each do |z|
        f.puts z
      end
    end

I would like to share my experience with `\n`  
I came to notice that &quot;\n&quot; works as-

    puts &quot;\n\n&quot; // to provide 2 new lines

but not

    p &quot;\n\n&quot;

also 
puts `&#39;\n\n&#39;`   
Doesn&#39;t works.

Hope will work for you!!

Actually you don&#39;t even need the block:


      Dir.chdir &#39;C:/Users/name/Music&#39;
      music = Dir[&#39;C:/Users/name/Music/*.{mp3, MP3}&#39;]
      puts &#39;what would you like to call the playlist?&#39;
      playlist_name = gets.chomp + &#39;.m3u&#39;
    
      File.open(playlist_name, &#39;w&#39;).puts(music)

Is there a more concise, efficient or simply pythonic way to do the following?

    def product(lst):
        p = 1
        for i in lst:
            p *= i
        return p

EDIT:

I actually find that this is marginally faster than using operator.mul:

    from operator import mul
    # from functools import reduce # python3 compatibility

    def with_lambda(lst):
	    reduce(lambda x, y: x * y, lst)

    def without_lambda(lst):
	    reduce(mul, lst)

    def forloop(lst):
	    r = 1
	    for x in lst:
	      	r *= x
	    return r

    import timeit

    a = range(50)
    b = range(1,50)#no zero
    t = timeit.Timer(&quot;with_lambda(a)&quot;, &quot;from __main__ import with_lambda,a&quot;)
    print(&quot;with lambda:&quot;, t.timeit())
    t = timeit.Timer(&quot;without_lambda(a)&quot;, &quot;from __main__ import without_lambda,a&quot;)
    print(&quot;without lambda:&quot;, t.timeit())
    t = timeit.Timer(&quot;forloop(a)&quot;, &quot;from __main__ import forloop,a&quot;)
    print(&quot;for loop:&quot;, t.timeit())

    t = timeit.Timer(&quot;with_lambda(b)&quot;, &quot;from __main__ import with_lambda,b&quot;)
    print(&quot;with lambda (no 0):&quot;, t.timeit())
    t = timeit.Timer(&quot;without_lambda(b)&quot;, &quot;from __main__ import without_lambda,b&quot;)
    print(&quot;without lambda (no 0):&quot;, t.timeit())
    t = timeit.Timer(&quot;forloop(b)&quot;, &quot;from __main__ import forloop,b&quot;)
    print(&quot;for loop (no 0):&quot;, t.timeit())

gives me

    (&#39;with lambda:&#39;, 17.755449056625366)
    (&#39;without lambda:&#39;, 8.2084708213806152)
    (&#39;for loop:&#39;, 7.4836349487304688)
    (&#39;with lambda (no 0):&#39;, 22.570688009262085)
    (&#39;without lambda (no 0):&#39;, 12.472226858139038)
    (&#39;for loop (no 0):&#39;, 11.04065990447998)

Returning the product of a list

PHP has an ``intval()`` function that will convert a string to an integer. However I want to check that the string is an integer beforehand, so that I can give a helpful error message to the user if it&#39;s wrong. PHP has ``is_int()``, but that returns false for string like ``&quot;2&quot;``.

PHP has the ``is_numeric()`` function, but that will return true if the number is a double. I want something that will return false for a double, but true for an int.

e.g.:

    my_is_int(&quot;2&quot;) == TRUE
    my_is_int(&quot;2.1&quot;) == FALSE

How to check that a string is an int, but not a double, etc.?

How do I make `\n` actually work in my output? At the moment it just writes it all in 1 long block. Thanks for any help

    Dir.chdir &#39;C:/Users/name/Music&#39;
    music = Dir[&#39;C:/Users/name/Music/*.{mp3, MP3}&#39;]
    puts &#39;what would you like to call the playlist?&#39;
    @new = &#39;&#39;
    playlist_name = gets.chomp + &#39;.m3u&#39;
    
    music.each do |z|
      @new += z + &#39;\n&#39;
    end
    	
    File.open playlist_name, &#39;w&#39; do |f|
      f.write @new
    end

How to do a newline in output

How do I make <code>\n</code> actually work in my output? At the moment it just writes it all in 1 long block. Thanks for any help
<pre><code class="hljs language-arduino">Dir.chdir 'C:/Users/name/Music'
music = Dir['C:/Users/name/Music/*.{mp3, MP3}']
puts 'what would you like to call the playlist?'
@new = ''
playlist_name = gets.chomp + '.m3u'

music.each do |z|
 @new += z + '\n'
end
	
File.open playlist_name, 'w' do |f|
 f.write @new
end
</code></pre>

I tried to iterate backwards with using a Range and `each`:

    (4..0).each do |i|
      puts i
    end
    ==&gt; 4..0

Iteration through `0..4` writes the numbers. On the other Range `r = 4..0` seems to be ok, `r.first == 4`, `r.last == 0`.

It seems to be strange to me that the construct above does not produce the expected result. What is the a reason for that? What are the situations when this behaviour is reasonable?


Is there a reason that we cannot iterate on &quot;reverse Range&quot; in ruby?

You can dynamically define a class method for a class like so:

    class Foo
    end

    bar = %q{def bar() &quot;bar!&quot; end}
    Foo.instance_eval(bar)


But how do you do the opposite: ***remove/undefine*** a class method? I suspect Module&#39;s `remove_method` and `undef_method` methods might be able to be used for this purpose, but all of the examples I&#39;ve seen after Googling for hours have been for removing/undefining *instance* methods, not class methods. Or perhaps there&#39;s a syntax you can pass to `instance_eval` to do this as well.

Thanks in advance.

Remove/undef a class method

What&#39;s the difference between the `or` and `||` operators in Ruby? Or is it just preference?

Difference between &quot;or&quot; and || in Ruby?

I&#39;m probably missing something obvious, but is there a way to access the index/count of the iteration inside a hash each loop?

    hash = {&#39;three&#39; =&gt; &#39;one&#39;, &#39;four&#39; =&gt; &#39;two&#39;, &#39;one&#39; =&gt; &#39;three&#39;}
    hash.each { |key, value| 
        # any way to know which iteration this is
        #   (without having to create a count variable)?
    }

Possible to access the index in a Hash each loop?

Suppose you&#39;re in your users controller and you want to get a json response for a show request, it&#39;d be nice if you could create a file in your views/users/ dir, named show.json and after your users#show action is completed, it renders the file.

Currently you need to do something along the lines of:

    def show
      @user = User.find( params[:id] )
      respond_to do |format|
        format.html
        format.json{
          render :json =&gt; @user.to_json
        }
      end
    end

But it would be nice if you could just create a show.json file which automatically gets rendered like so:

    def show
      @user = User.find( params[:id] )
      respond_to do |format|
        format.html
        format.json
      end
    end

This would save me tons of grief, and would wash away that horribly dirty feeling I get when I render my json in the controller

In Rails, how do you render JSON using a view?

How can I replace all line breaks from a string in Java in such a way that will work on Windows and Linux (ie no OS specific problems of carriage return/line feed/new line etc.)?

I&#39;ve tried (note readFileAsString is a function that reads a text file into a String):    		

    String text = readFileAsString(&quot;textfile.txt&quot;);
    text.replace(&quot;\n&quot;, &quot;&quot;);

but this doesn&#39;t seem to work.

How can this be done?

How to remove line breaks from a file in Java?

I would like to get an istream_iterator&lt;string&gt;-style iterator that returns each line of the file as a string rather than each word.  Is this possible?

Is there a C++ iterator that can iterate over a file line by line?

Let see that I have a string look like this:   

    NSString *longStr = @&quot;AAAAA\nBBBBB\nCCCCC&quot;;  

How do I make it so that the UILabel display the message like this   

&gt; AAAAA&lt;br /&gt;
&gt; BBBBB&lt;br /&gt;
&gt; CCCCC

I don&#39;t think `\n` is recognized by UILabel, so is there anything that I can put inside NSString so that UILabel knows that it has to create a line break there?

How to add line break for UILabel?

Does anyone know how to use line breaks in NSString? I need to do something like this -

    [NSString stringWithFormat:@&quot;%@,\n%@&quot;, mystring1,mystring2];


NSString with \n or line break

How can I write to files using Python (on Windows) and use the Unix end of line character?

e.g. When doing:
&lt;pre&gt;
f = open(&#39;file.txt&#39;, &#39;w&#39;)
f.write(&#39;hello\n&#39;)
f.close()
&lt;/pre&gt;
Python automatically replaces `\n` with `\r\n`.

Content Type	Original Author	Original Content on Stackoverflow
Question	babyrats	View Question on Stackoverflow
Solution 1 - Ruby	kjagiello	View Answer on Stackoverflow
Solution 2 - Ruby	Ben	View Answer on Stackoverflow
Solution 3 - Ruby	S.Yadav	View Answer on Stackoverflow
Solution 4 - Ruby	Tim Breitkreutz	View Answer on Stackoverflow

How to do a newline in output

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

Solution 3 - Ruby

Solution 4 - Ruby

How to check that a string is an int, but not a double, etc.?

Returning the product of a list

Attributions