The `%s` specifier converts the object using [`str()`][1], and `%r` converts it using [`repr()`][2].

For some objects such as integers, they yield the same result, but [`repr()`][2] is special in that (for types where this is possible) it conventionally returns a result that is valid Python syntax, which could be used to unambiguously recreate the object it represents.

Here&#39;s an example, using a date:

    &gt;&gt;&gt; import datetime
    &gt;&gt;&gt; d = datetime.date.today()
    &gt;&gt;&gt; str(d)
    &#39;2011-05-14&#39;
    &gt;&gt;&gt; repr(d)
    &#39;datetime.date(2011, 5, 14)&#39;

Types for which [`repr()`][2] doesn&#39;t produce Python syntax include those that point to external resources such as a `file`, which you can&#39;t guarantee to recreate in a different context.


  [1]: https://docs.python.org/2/library/functions.html#str
  [2]: https://docs.python.org/2/library/functions.html#repr

Use the `%r` for debugging, since it displays the &quot;raw&quot; data of the variable, 
but the others are used for displaying to users.

That&#39;s how `%r` formatting works; it prints it the way you wrote it (or close to it). It&#39;s the &quot;raw&quot; format for debugging. Here `\n` used to display to users doesn&#39;t work. `%r` shows the representation if the raw data of the variable.

    months = &quot;\nJan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug&quot;
    print &quot;Here are the months: %r&quot; % months

Output:

&lt;!-- language: lang-none --&gt;

    Here are the months: &#39;\nJan\nFeb\nMar\nApr\nMay\nJun\nJul\nAug&#39;

Check [this example](http://learnpythonthehardway.org/book/ex6.html) from Learn Python the Hard Way.

`%r` shows with quotes:

It will be like:

    I said: &#39;There are 10 types of people.&#39;.

If you had used `%s` it would have been:

    I said: There are 10 types of people..
   

This is a version of Ben James&#39;s answer, above:

    &gt;&gt;&gt; import datetime
    &gt;&gt;&gt; x = datetime.date.today()
    &gt;&gt;&gt; print x
    2013-01-11
    &gt;&gt;&gt; 
    &gt;&gt;&gt; 
    &gt;&gt;&gt; print &quot;Today&#39;s date is %s ...&quot; % x
    Today&#39;s date is 2013-01-11 ...
    &gt;&gt;&gt; 
    &gt;&gt;&gt; print &quot;Today&#39;s date is %r ...&quot; % x
    Today&#39;s date is datetime.date(2013, 1, 11) ...
    &gt;&gt;&gt;

When I ran this, it helped me see the usefulness of %r. 

In Rails we can do the following in case a value doesn&#39;t exist to avoid an error:

    @myvar = @comment.try(:body)

What is the equivalent when I&#39;m digging deep into a hash and don&#39;t want to get an error?

    @myvar = session[:comments][@comment.id][&quot;temp_value&quot;] 
    # [:comments] may or may not exist here

In the above case, `session[:comments]try[@comment.id]` doesn&#39;t work. What would?

Equivalent of .try() for a hash to avoid &quot;undefined method&quot; errors on nil?

From my experience, a php server would throw an exception to the log or to the server end, but node.js just simply crashes. Surrounding my code with a try-catch doesn&#39;t work either since everything is done asynchronously. I would like to know what does everyone else do in their production servers.

How do I prevent node.js from crashing? try-catch doesn&#39;t work

On [Learn Python the Hard Way](http://learnpythonthehardway.org/) page 21, I see this code example:

    x = &quot;There are %d types of people.&quot; % 10
    ...
    print &quot;I said: %r.&quot; % x

Why is `%r` used here instead of `%s`?  When would you use `%r`, and when would you use `%s`?

When to use %r instead of %s in Python?

On <a href="http://learnpythonthehardway.org/" target="_blank" rel="noopener noreferrer">Learn Python the Hard Way</a> page 21, I see this code example:
<pre><code class="hljs language-perl">x = "There are %d types of people." % 10
...
print "I said: %r." % x
</code></pre>
Why is <code>%r</code> used here instead of <code>%s</code>? When would you use <code>%r</code>, and when would you use <code>%s</code>?

I have something like this:

    text = &#39;This text is very very long.&#39;
    replace_words = [&#39;very&#39;,&#39;word&#39;]
   
    for word in replace_words:
        text = text.replace(&#39;very&#39;,&#39;not very&#39;)



I would like to only replace the first &#39;very&#39; or choose which &#39;very&#39; gets overwritten. I&#39;m doing this on much larger amounts of text so I want to control how duplicate words are being replaced.

Replace first occurrence only of a string?

I&#39;am tasked with converting tons of .doc files to .pdf. And the only way my supervisor wants me to do this is through MSWord 2010. I know I should be able to automate this with python COM automation. Only problem is I dont know how and where to start. I tried searching for some tutorials but was not able to find any (May be I might have, but I don&#39;t know what I&#39;m looking for). 

Right now I&#39;m reading through [this][1]. Dont know how useful this is going to be.


  [1]: http://oreilly.com/catalog/pythonwin32/chapter/ch12.html#49339

.doc to pdf using python

I have a Mac running Python 2.6. When I try to use `easy_install` I get this message:

    /usr/bin/easy_install-2.6:7: UserWarning: Module pkg_resources was already imported from /System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.pyc, but /Library/Python/2.6/site-packages is being added to sys.path
      from pkg_resources import load_entry_point
    /usr/bin/easy_install-2.6:7: UserWarning: Module site was already imported from /System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site.pyc, but /Library/Python/2.6/site-packages is being added to sys.path
      from pkg_resources import load_entry_point
    Traceback (most recent call last):
      File &quot;/usr/bin/easy_install-2.6&quot;, line 10, in &lt;module&gt;
        load_entry_point(&#39;setuptools==0.6c9&#39;, &#39;console_scripts&#39;, &#39;easy_install&#39;)()
      File &quot;/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py&quot;, line 271, in load_entry_point
        return False
      File &quot;/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py&quot;, line 2173, in load_entry_point
        deps = []
    ImportError: Entry point (&#39;console_scripts&#39;, &#39;easy_install&#39;) not found

I am very confused by this and I want to know how I can fix this. Previously I didn&#39;t get this message, then after installing `pip` and uninstalling it, easy_install no longer works. I was wondering how I could fix this, or restore the default Python or easy_install setting on Mac.


Why is Python easy_install not working on my Mac?

I need to insert rows into PG one of the fields is date and time with time stamp, this is the time of incident, so I can not use --&gt; current_timestamp function of Postgres at the time of insertion, so how can I then insert the time and date which I collected before into pg row in the same format as it would have been created by current_timestamp at that point in time.


How to insert current_timestamp into Postgres via python

How can I access captured groups if I do `findall(r&#39;regex(with)capturing.goes.here&#39;)` ?
I know I can do it through `finditer`, but I don&#39;t want to iterate.

Capturing group with findall?

I wanted to ask about a specific point made in Effective C++. 

It says:

&gt; A destructor should be made virtual if a class needs to act like a polymorphic class. It further adds that since `std::string` does not have a virtual destructor, one should never derive from it. Also `std::string` is not even designed to be a base class, forget polymorphic base class. 

I do not understand what specifically is required in a class to be eligible for being a base class (not a polymorphic one)?

Is the only reason that I should not derive from `std::string` class is it does not have a virtual destructor? For reusability purpose a base class can be defined and multiple derived class can inherit from it. So what makes `std::string` not even eligible as a base class?

Also, if there is a base class purely defined for reusability purpose and there are many derived types, is there any way to prevent client from doing `Base* p = new Derived()` because the classes are not meant to be used polymorphically?

Why should one not derive from c++ std string class?

I need to get the last part of current directory, for example  from `/Users/smcho/filegen_from_directory/AIRPassthrough`, I need to get `AIRPassthrough`. 

With python, I can get it with this code.

    import os.path
    
    path = &quot;/Users/smcho/filegen_from_directory/AIRPassthrough&quot;
    print os.path.split(path)[-1]

Or

    print os.path.basename(path)

How can I do the same thing with C#?

## ADDED
With the help from the answerers, I found what I needed.

    using System.Linq;
    string fullPath = Path.GetFullPath(fullPath).TrimEnd(Path.DirectorySeparatorChar);
    string projectName  = fullPath.Split(Path.DirectorySeparatorChar).Last();

or 

    string fullPath = Path.GetFullPath(fullPath).TrimEnd(Path.DirectorySeparatorChar);
    string projectName = Path.GetFileName(fullPath);

Get the (last part of) current directory name in C#

I am using R to parse a list of strings in the form:

    original_string &lt;- &quot;variable_name=variable_value&quot;

First, I extract the variable name and value from the original string and convert the value to numeric class. 

    parameter_value &lt;- as.numeric(&quot;variable_value&quot;)
    parameter_name &lt;- &quot;variable_name&quot;
    
Then, I would like to assign the value to a variable with the same name as the `parameter_name` string.

    variable_name &lt;- parameter_value

What is/are the function(s) for doing this?

Convert string to a variable name

Does anyone know of a regular expression I could use to find URLs within a string? I&#39;ve found a lot of regular expressions on Google for determining if an entire string is a URL but I need to be able to search an entire string for URLs.  For example, I would like to be able to find `www.google.com` and `http://yahoo.com` in the following string:

&lt;!-- Language: none --&gt;

    Hello www.google.com World http://yahoo.com

I am not looking for specific URLs in the string. I am looking for ALL of the URLs in the string which is why I need a regular expression.

Regular expression to find URLs within a string

I am wondering if it is possible, using the String.format method in Java, to give an integer preceding zeros?

For example:

1 would become 001&lt;br/&gt;
2 would become 002&lt;br/&gt;
...&lt;br/&gt;
11 would become 011&lt;br/&gt;
12 would become 012&lt;br/&gt;
...&lt;br/&gt;
526 would remain as 526&lt;br/&gt;
...etc&lt;br/&gt;

At the moment I have tried the following code:

    String imageName = &quot;_%3d&quot; + &quot;_%s&quot;;

    for( int i = 0; i &lt; 1000; i++ ){
        System.out.println( String.format( imageName, i, &quot;foo&quot; ) );
    }

Unfortunately, this precedes the number with 3 empty spaces. Is it possible to precede the number with zeros instead?



Format an Integer using Java String Format

If I do this in C#:

    Console.WriteLine(DateTime.Now.ToString(&quot;ddd M/dd/yy&quot;));

I would expect output like this:

    Wed 6/15/11

But it actually outputs this:

    Wed 6 15 11

Why are the slashes disappearing? Is there a way to prevent this and have the date outputted in the expected format?

C# date formatting is losing slash separators

Primitive question, but how do I format strings like this:

&gt; &quot;Step {1} of {2}&quot;

 by substituting variables using Java? In C# it&#39;s easy.

How to format strings in Java

I have a function to add commas to numbers:

    function commafy( num ) {
      num.toString().replace( /\B(?=(?:\d{3})+)$/g, &quot;,&quot; );
    }

Unfortunately, it doesn&#39;t like decimals very well. Given the following usage examples, what is the best way to extend my function?


    commafy( &quot;123&quot; )                 // &quot;123&quot;
    commafy( &quot;1234&quot; )                // &quot;1234&quot;
                                     // Don&#39;t add commas until 5 integer digits
    commafy( &quot;12345&quot; )               // &quot;12,345&quot;
    commafy( &quot;1234567&quot; )             // &quot;1,234,567&quot;
    commafy( &quot;12345.2&quot; )             // &quot;12,345.2&quot;
    commafy( &quot;12345.6789&quot; )          // &quot;12,345.6789&quot;
                                     // Again, nothing until 5
    commafy( &quot;.123456&quot; )             // &quot;.123 456&quot;
                                     // Group with spaces (no leading digit)
    commafy( &quot;12345.6789012345678&quot; ) // &quot;12,345.678 901 234 567 8&quot;

Presumably the easiest way is to first split on the decimal point (if there is one). Where best to go from there?


Add commas or spaces to group every three digits


    String hello = &quot;Hello&quot;;
    
    String.format(&quot;%s %s %s %s %s %s&quot;, hello, hello, hello, hello, hello, hello);

    hello hello hello hello hello hello 

Does the `hello` variable need to be repeated multiple times in the call to the format method or is there a shorthand version that lets you specify the argument once to be applied to all of the `%s` tokens?

Content Type	Original Author	Original Content on Stackoverflow
Question	coffee-grinder	View Question on Stackoverflow
Solution 1 - Python	Ben James	View Answer on Stackoverflow
Solution 2 - Python	Pramod Bhat	View Answer on Stackoverflow
Solution 3 - Python	manojlds	View Answer on Stackoverflow
Solution 4 - Python	macloo	View Answer on Stackoverflow

When to use %r instead of %s in Python?

Python Problem Overview

Python Solutions

Solution 1 - Python

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How do I prevent node.js from crashing? try-catch doesn't work

Equivalent of .try() for a hash to avoid "undefined method" errors on nil?

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