python - Matplotlib: TypeError: 'AxesSubplot' object is not callable -

i new programming please pardon me if rookie mistake.

i writing python script have defined functions create subplots of distributions.

i have slider widget end user change value of variables(mu , sigma) , see effect on distribution. here's code

import numpy np print np.__version__ import scipy print scipy.__version__ scipy.stats import norm, lognorm, uniform import matplotlib print matplotlib.__version__ import matplotlib.pyplot plt matplotlib.widgets import slider, button, radiobuttons, checkbuttons    #####calculating mean , standard deviation#####  global mu_a1 mu_a1 = 1 global mu_b1 mu_b1 = 10 global mu_c1 mu_c1 = -13 global sigma_a1 sigma_a1 =  0.14 global sigma_b1 sigma_b1 =  1.16 global sigma_c1 sigma_c1 =  2.87 mu_x01 = -11 sigma_x01 =  1.9  #####_____#####    #####generating random data#####  a1 = 0.75*mu_a1 + (1.25 - 0.75)*sigma_a1*np.random.sample(10000) b1 = 8*mu_b1 + (12 - 8)*sigma_b1*np.random.sample(10000) c1 = -12*mu_c1 + 2*sigma_c1*np.random.sample(10000) x01 = (-b1 - np.sqrt(b1**2 - (4*a1*c1)))/(2*a1)  #####_____#####    #######creating subplots & plotting distributions#####  fig = plt.figure() plt.subplots_adjust(left=0.13,right=0.99,bottom=0.05)  def ax1():     ax1 = fig.add_subplot(331)     ax1.clear()     ax1.set_xlabel('a' , fontsize = 14)     ax1.grid(true)     [n1,bins1,patches] = ax1.hist(a1, bins=50, color = 'red',alpha = 0.5, normed = true)     return ax1  def ax2():     ax2 = fig.add_subplot(334)     ax2.clear()     ax2.set_xlabel('b' , fontsize = 14)     ax2.grid(true)     [n2,bins2,patches] = ax2.hist(b1, bins=50, color = 'red',alpha = 0.5, normed = true)     return ax2  def ax3():     ax3 = fig.add_subplot(337)     ax3.clear()     ax3.set_xlabel('c' , fontsize = 14)     ax3.grid(true)     [n3,bins3,patches] = ax3.hist(c1, bins=50, color = 'red',alpha = 0.5, normed = true)     return ax3  def ax4_ax5():     ax4 = fig.add_subplot(132)     ax4.clear()     ax4.set_xlabel('x0' , fontsize = 14)     ax4.grid(true)     [n4,bins4,patches] = ax4.hist(x01, bins=50, color = 'red',alpha = 0.5, normed = true)     ax4.axvline(np.mean(x01), color = 'black', linestyle = 'dashed', lw = 2)      ax5 = fig.add_subplot(133)     ax5.clear()     ax5.set_xlabel('x0' , fontsize = 14)     ax5.set_ylabel('cdf', fontsize = 14)     ax5.grid(true)     dx = bins4[1] - bins4[0]     cdf = np.cumsum(n4)*dx     ax5.plot(bins4[1:], cdf, color = 'red')     return ax4,ax5  #######_____#####  ax1 = ax1() ax2 = ax2() ax3 = ax3() ax4, ax5 = ax4_ax5()  #####creating sliders#####  axcolor = 'lightgoldenrodyellow' axmu_331 = plt.axes([0.015, 0.67, 0.07, 0.015], axisbg=axcolor) axsigma_331 = plt.axes([0.015, 0.65, 0.07, 0.015], axisbg=axcolor) smu_331 = slider(axmu_331, 'm', -13.0 , 10.0, valinit = 1.0) ssigma_331 = slider(axsigma_331, 'sd', -3.0 , 3.0, valinit =1.0)  #####_____#####    #####updating sliders#####  def update_slider_331(val):     mu_a1 = smu_331.val     print mu_a1     sigma_a1 = ssigma_331.val     print sigma_a1     ax1()     ax4_ax5()     plt.draw()  smu_331.on_changed(update_slider_331) ssigma_331.on_changed(update_slider_331)  #####_____#####   plt.show() 

i distribution update every time slider value changed . however, when change slider value, error

  traceback (most recent call last):   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\backends\backend_qt4.py", line 175, in mousepressevent     figurecanvasbase.button_press_event( self, x, y, button )   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\backend_bases.py", line 1632, in button_press_event     self.callbacks.process(s, mouseevent)   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\cbook.py", line 262, in process     proxy(*args, **kwargs)   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\cbook.py", line 192, in __call__     return mtd(*args, **kwargs)   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\widgets.py", line 315, in _update     self.set_val(val)   file "c:\program files (x86)\python27\lib\site-packages\matplotlib\widgets.py", line 327, in set_val     func(val)   file "h:/uq&m/gui demos/wip/stack overflow_func.py", line 118, in update_slider_331     ax1() typeerror: 'axessubplot' object not callable 

i have mouse click event (not shown in above code) call 'ax' functions , work fine. wondering why not working slider update function.

thanks in advance :-)