title: How do I fix Bowtie and Python Error (Errno2)?
body: <p>I am trying to repeat the "Indexing a reference genome" step of <a href="http://bowtie-bio.sourceforge.net/bowtie2/manual.shtml#building-from-source" rel="nofollow noreferrer">this</a> tutorial.</p>
  
  <p>However, when I run the command</p>
  
  <p><code>../bowtie2-master/bowtie2-build ./bowtie2-master/example/reference/lambda_virus.fa lambda_virus</code></p>
  
  <p>This error happens:</p>
  
  <pre><code>  File "../bowtie2-master/bowtie2-build", line 90, in &lt;module&gt;
      main()
    File "../bowtie2-master/bowtie2-build", line 87, in main
      sys.exit(subprocess.call(list(argv)))
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 172, in call
      return Popen(*popenargs, **kwargs).wait()
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 394, in __init__
      errread, errwrite)
    File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1047, in _execute_child
      raise child_exception
  OSError: [Errno 2] No such file or directory
  
  </code></pre>
  
  <p>Output of <code>pwd</code>:</p>
  
  <pre><code>/Users/ltelles/Desktop/documents_desktop/bioinformatics/bowtie2_example_project
  </code></pre>
  
  <p>What is going on and how can I fix it? Thank's!</p>