title: How to recursively go through all subdirectories and read files?
body: <p>I have a root-ish directory containing multiple subdirectories, all of which contain a file name data.txt. What I would like to do is write a script that takes in the "root" directory, and then reads through all of the subdirectories and reads every "data.txt" in the subdirectories, and then writes stuff from every data.txt file to an output file.</p>
  
  <p>Here's a snippet of my code:</p>
  
  <pre><code>import os
  import sys
  rootdir = sys.argv[1]
  
  with open('output.txt','w') as fout:
      for root, subFolders, files in os.walk(rootdir):
          for file in files:
              if (file == 'data.txt'):
                  #print file
                  with open(file,'r') as fin:
                      for lines in fin:
                          dosomething()
  </code></pre>
  
  <p>My dosomething() part -- I've tested and confirmed for it to work if I am running that part just for one file. I've also confirmed that if I tell it to print the file instead (the commented out line) the script prints out 'data.txt'.</p>
  
  <p>Right now if I run it Python gives me this error: </p>
  
  <pre><code>File "recursive.py", line 11, in &lt;module&gt;
      with open(file,'r') as fin:
  IOError: [Errno 2] No such file or directory: 'data.txt'
  </code></pre>
  
  <p>I'm not sure why it can't find it -- after all, it prints out data.txt if I uncomment the 'print file' line. What am I doing incorrectly?</p>