title: 'numpy.float64' object is not callable
body: <p>For some reason that I can't wrap my head around, it says <code>TypeError: 'numpy.float64' object is not callable</code> for the following code:</p>
  
  <pre><code>import pylab as pl
  import scipy as sp
  import numpy as num
  
  import scipy.integrate as spi
  import matplotlib.pyplot as mat
  import scipy.optimize as spo
  from itertools import cycle
  from matplotlib.font_manager import FontProperties
  
  rs=.14
  ra=0.0027
  Mz=91.
  ja=0.81
  js=-.033
  Gz=2.5
  k=10**6
  def sig_a(s,Gz):
      return (sp.pi)*((s*ra+(s-Mz**2)*ja)/((s-Mz**2)**2+Mz**2*Gz**2))
  def sig_s(s,Gz):
      return (4*sp.pi/3)*(1/s+(s*rs+(s-Mz**2)*js)/((s-Mz**2)**2+Mz**2*Gz**2))
  
  cos_theta=num.arange(-0.95,0.95,0.05)
  E=num.arange(20,140,.1)
  s=E**2
  
  
  def f_theta(x,s):
      ans=k*(sig_s(s,Gz)*(1+(x)**2)+sig_a(s,Gz)*x)
      return and
  
  
  d=num.arange(0.05,1.80,0.25)
  x1=[]
  for t in cos_theta:
      m=((t+t+0.05)/2)
      x1.append(m)
  x01=num.array(x1)
  def N_mu1(x0,sig_a,sig_s):     #&lt;-------d=0.05
      n=(k*(sig_s*((x0**2.)*0.05+(0.05/4.)+(0.05**3.)/(12.))+sig_a(2.*x0*0.05)))
      return n
  
  idealN=[]
  randomN=[]
  est_sig_a=[]
  est_sig_s=[]
  ratio_error=[]     
  for i in s:
      for j in cos_theta:
          n=(spi.quad(f_theta,j,j+0.05,args=i))
          idealN.append(n[0])
      for k in idealN:
          r=num.random.poisson(k,1)
          randomN.append(r[0])
      siga=sig_a(i,Gz)
      sigs=sig_s(i,Gz)
      R=num.array(randomN)
      Error=(R**0.5)
      po,po_cov=spo.curve_fit(N_mu1,x01,R,[siga,sigs],Error)
      est_sig_a.append(po[0])
      est_sig_s.append(po[1])
      e=((((po_cov[0])/(po[0]))+((po_cov[1])/(po[1])))*((po[0])/(po[1])))
      ratio_error.append(e)
      idealN=[]
      randomN=[]
  </code></pre>
  
  <p>And the error show was:</p>
  
  <pre><code>TypeError                                 Traceback (most recent call last)
      118     R=num.array(randomN)
      119     error=(R**0.5)
  --&gt; 120     po,po_cov=spo.curve_fit(N_mu1,x01,R,[siga,sigs],error)
      121     est_sig_a.append(po[0])
      122     est_sig_s.append(po[1])
  
  
  TypeError: 'numpy.float64' object is not callable
  </code></pre>
  
  <p>I am struggling to find the mistake in the code. </p>