title: ValueError: zero length field name in format python
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/5446964/valueerror-zero-length-field-name-in-format-error-in-python-3-0-3-1-3-2">&ldquo;ValueError: zero length field name in format&rdquo; error in Python 3.0,3.1,3.2</a>  </p>
  </blockquote>
  
  
  
  <p>I have spent hours trying to solve this problem but to no avail. I read <a href="http://docs.python.org/release/3.1.3/library/string.html" rel="noreferrer">this guide</a>.
  I haven't found any examples how to do what I need. </p>
  
  <p>When I run the script I get this error (partly omitted):<br></p>
  
  <pre><code>Traceback (...):
     [...]
     output.write("{: &gt; 026,.18e} {: &gt; 026,.18e}\n".format(x,y))
  ValueError: zero length field name in format.
  </code></pre>
  
  <p>The code is written in python 2.6 or 2.7 but I run python 3.1. How would I need to change output format so that it would work? </p>
  
  <pre><code>def f(x,y,a = 0.01):
      return y/(a+x)-y**3
  
  def ekspEuler(N,dat):
      output = open(dat,"w")
      h = 3.0/N
      x,y = 0,1 #zac.pogoj
  
      for i in range(1,N+2):
          output.write("{: &gt; 026,.18e} {: &gt; 026,.18e}\n".format(x,y))
          y += h*f(x,y)
          x = i*h
      output.close()
  </code></pre>
  
  <p>Thanks for your help.</p>