title: Strange error with matplotlib axes labels
body: <p>I'm very new to Python and programming in general, so apologies in advance if I'm missing something obvious. I'm trying to plot a graph and label the axes, but every time I try to label the y axis an exception is raised. I wrote the code below in a new script to make sure the problem wasn't coming from somewhere else in the module. I'm using Python 3.4.</p>
  
  <pre><code>from numpy import *
  from matplotlib import *
  
  a = [1, 2, 3, 4, 5]
  b = [2, 3, 2, 3, 2]
  pyplot.plot(a, b)
  pylab.xlabel("Time")
  pylab.ylabel("Speed")
  </code></pre>
  
  <p>Every time, I get the error 'TypeError: 'str' object is not callable' for the final line. If I change the y to an x, everything is fine. If I change the x to a y, I get the same error. However, ylabel comes up on the drop down list for ylabel so the function does exist and the documentation says a string is the only necessary argument, exactly as for xlabel (matplotlib.pyplot.ylabel(s, *args, **kwargs) and matplotlib.pyplot.xlabel(s, *args, **kwargs)). What on earth could be going on here?</p>