What is the proper way to take a directory path as user input?

Question

Below is a snippet of code I am trying to use to take a directory path as "raw input" from the user. I receive the following error after the input is taken from the user:

Traceback (most recent call last):
  File "C:\Users\larece.johnson\Desktop\Python Programs\Hello World 2", line 14, in <module>
    f = open(str,"r+")                                     #I open the text file here which the user gave me
IOError: [Errno 2] No such file or directory: 'C:/Users/larece.johnson/Desktop/Python Programs/BostonLog.log.2014-04-01'

Ignoring what I have done below, is there a particular way I am supposed to take the path from user so that Python accepts it?

For example, the directory and file I'm looking for is

C:/Users/larece.johnson/Desktop/Python Programs/BostonLog.log.2014-04-01

import re     #this library is used so that I can use the "search" function
import os     #this is needed for using directory paths and manipulating them 

str =""       #initializing string variable for raw data input

#print os.getcwd()
#f = open("C:/Users/larece.johnson/Desktop/BostonLog.log.2014-04-02.log","r+")

str = raw_input("Enter the name of your text file - please use / backslash when typing in directory path: ");  #User will enter the name of text file for me

f = open(str,"r+")

Answer 1

I think you should try something like:

    import sys
    import os

    user_input = input("Enter the path of your file: ")
     
    assert os.path.exists(user_input), "I did not find the file at, "+str(user_input)
    f = open(user_input,'r+')
    print("Hooray we found your file!")
    #stuff you do with the file goes here
    f.close()

Answer 2

It seems you want to check if the directory exists.

If so, see os.path.isdir.

os.path.isdir(path)
    Return True if path is an existing directory.
    This follows symbolic links, so both islink()
    and isdir() can be true for the same path.

You can do like this:

s = raw_input();
if os.path.isdir(s):
    f = open(s, "r+")
else:
    print "Directory not exists."