title: why is there this TypeError?
body: <p>i am trying to find the square root a number through the function sqrt(a). fixedPoint(f, epsilon) is a helper function. the problem is that i get a this TypeError: 'float' object is not callable. i am new to programming, so if anybody can help and find were is the bug and explain what does this error mean ??</p>
  
  <pre><code>def fixedPoint(f, epsilon):
      """
      f: a function of one argument that returns a float
      epsilon: a small float
  
      returns the best guess when that guess is less than epsilon 
      away from f(guess) or after 100 trials, whichever comes first.
      """
      guess = 1.0
      for i in range(100):
          if abs(f(guess) - guess) &lt; epsilon:
              return guess
          else:
              guess = f(guess)
      return guess
  
  
  def sqrt(a):
      def tryit(x):
          return 0.5 * (a/x + x)
      return fixedPoint(tryit(a), 0.0001)
  </code></pre>