Calculator

import matplotlib.pyplot as plt
import numpy as np
import sympy as sp

#ENTERING THE WINDOW BOUNDS:
start = float(raw_input('enter lower x value; x = '))
end = float(raw_input('enter upper x value; x = '))
start1 = float(raw_input('enter lower y value; y = '))
end1 = float(raw_input('enter upper y value; y = '))

#GRAPHING THE ORIGINAL FUNCTION:
x = np.linspace(start, end, 20000)
d = raw_input("enter function here; y = ")
y = eval(str(d))
plt.plot(x,y,'-k')

#DIFFERENTIATING THE ORIGINAL FUNCTION:
x = sp.Symbol('x')
c = raw_input('enter function without the numpy; y = ')
dydx = sp.diff(c, x)
print dydx
t = dydx

#GRAPHING DY/DX:
x = np.linspace(start,end,20000)
z = raw_input('copy & paste first derivative here with numpy; y = ')
a = eval(str(z))
plt.plot(x,a,'-b')

#DIFFERENTIATING DY/DX TO GET D2Y/DX2:
x = sp.Symbol('x')
d2xdy2 = sp.diff(t, x)
print d2xdy2

#GRAPHING D2Y/DX2:
x = np.linspace(start,end,20000)
L = raw_input('copy & paste second derivative here with numpy; y = ')
l = eval(str(L))
plt.plot(x,l,'-y')

#PLAN B FOR IDENTIFYING THE MAX AND MIN
#lol1 = (a<0)
#lol2 = (a>0)
#plt.plot(x[lol1], y[lol1], lw=3)
#plt.plot(x[lol2],y[lol2],linestyle='--', lw=5)


#MARKING CONCAVITY:
segment1 = (l<0)
segment2 = (l>0)
plt.plot(x[segment1], y[segment1], '-k', lw=1)
plt.plot(x[segment2], y[segment2], '-r', lw=1)

if t == float('inf') or t== float('inf'):
    plt.axvline(linewidth=4,color='cyan')
    plt.show()

plt.grid()
plt.xlim(start, end)
plt.ylim(start1,end1)

print 'original function when concave down = black'
print 'original function when concave up = red'
#print 'original function when increasing = dashed green line'
#print 'original function when decreasing = thick blue line'
print 'first derivative = blue'
print 'second derviative = yellow'

plt.show()