Python: Check folder directory given by user input
<p>I'm creating some python code, where its initial stage lets the user input the directory of a source folder, destination folder and a text file. These directories should be checked right after the user input. Here is an example how it should look like:</p>

<pre><code>Enter directory path of a source folder:
&gt;&gt;&gt;C:\bla\source_folder
Thanks, this folder exists.

Enter directory path of a destination folder:
&gt;&gt;&gt;C:\dest_folder            
</code></pre>

<blockquote>
  <p>(let's say this folder does not exist)</p>
</blockquote>

<pre><code>This folder does not exist! Please enter correct path.
&gt;&gt;&gt;C:\bla\dest_folder

Enter directory path of a text file:
&gt;&gt;&gt;C:\bla\bla.txt
Thanks, this file exists.
</code></pre>

<p>My code is <strong>incomplete</strong>, and probably <strong>wrong</strong>, because I really don't know how to do it.</p>

<pre><code>def source_folder()
    source_folder = raw_input("Enter path of source folder: ")
    try:
        if open(source_folder)
            print("Folder path is correct!")
    except:
        #if there are any errors, print 'fail' for these errors
        print(source_folder, 'This folder has not been found')

def dest_folder()
    dest_folder = raw_input("Enter path of destination folder: ")

def input_file()
    input_file = raw_input("Enter path of your text file: ")
</code></pre>