I am new to Python and trying to get this script to run, but it seems to be hanging in an infinite loop. When I use ctrl+c to stop it, it is always on line 103.
vs = 20.05 * np.sqrt(Tb + Lb * (y - y0)) # m/s speed of sound as a function of temperature
I am used to MatLab (from school) and the editor it has. I ran into issues earlier with the encoding for this code. Any suggestions on a (free) editor? I am currently using JEdit and/or Notepad.
Here is the full script:
#!/usr/bin/env python
# -*- coding: ANSI -*-
import numpy as np
from math import *
from astropy.table import Table
import matplotlib.pyplot as plt
from hanging_threads import start_monitoring#test for code hanging
start_monitoring(seconds_frozen=10, test_interval=100)
"""Initial Conditions and Inputs"""
d = 154.71/1000 # diameter of bullet (in meters)
m = 46.7 # mass of bullet ( in kg)
K3 = 0.87*0.3735 # drag coefficient at supersonic speed
Cd1 = 0.87*0.108 #drag coefficient at subsonic speed
v0 = 802 # muzzle velocity in m/sec
dt = 0.01 # timestep in seconds
"""coriolis inputs"""
L = 90*np.pi/180 # radians - latitude of firing site
AZ = 90*np.pi/180 # radians - azimuth angle of fire measured clockwise from North
omega = 0.0000727 #rad/s rotation of the earth
"""wind inputs"""
wx = 0 # m/s
wz = 0 # m/s
"""initializing variables"""
vx = 0 #initial x velocity
vy = 0 #initial y velocity
vy0 = 0
y_max = 0 #apogee
v = 0
t = 0
x = 0
"""Variable Atmospheric Pressure"""
rho0 = 1.2041 # density of air at sea-level (kg/m^3)
T = 20 #temperature at sea level in celcius
Tb = T + 273.15 # temperature at sea level in Kelvin
Lb = -2/304.8 # temperature lapse rate in K/m (-2degrees/1000ft)- not valid above 36000ft
y = 0 # current altitude
y0 = 0 # initial altitude
g = 9.81 # acceleration due to gravity in m/s/s
M = 0.0289644 #kg/mol # molar mass of air
R = 8.3144598 # J/molK - universal gas constant
# air density as a function of altitude and temperature
rho = rho0 * ((Tb/(Tb+Lb*(y-y0)))**(1+(g*M/(R*Lb))))
"""Variable Speed of Sound"""
vs = 20.05*np.sqrt(Tb +Lb*(y-y0)) # m/s speed of sound as a function of temperature
Area = pi*(d/2)**2 # computing the reference area
phi_incr = 5 #phi0 increment (degrees)
N = 12 # length of table
"""Range table"""
dtype = [('phi0', 'f8'), ('phi_impact', 'f8'), ('x', 'f8'), ('z', 'f8'),('y', 'f8'), ('vx', 'f8'), ('vz', 'f8'), ('vy', 'f8'), ('v', 'f8'),('M', 'f8'), ('t', 'f8')]
table = Table(data=np.zeros(N, dtype=dtype))
"""Calculates entire trajectory for each specified angle"""
for i in range(N):
phi0 = (i + 1) * phi_incr
"""list of initial variables used in while loop"""
t = 0
y = 0
y_max = y
x = 0
z = 0
vx = v0*np.cos(radians(phi0))
vy = v0*np.sin(radians(phi0))
vx_w = 0
vz_w = 0
vz = 0
v = v0
ay = 0
ax = 0
wx = wx
wz = wz
rho = rho0 * ((Tb / (Tb + Lb * (y - y0))) ** (1 + (g * M / (R * Lb))))
vs = 20.05 * np.sqrt(Tb + Lb * (y - y0)) # m/s speed of sound as a function of temperature
ax_c = -2 * omega * ((vz * sin(L)) + vy * cos(L) * sin(AZ))
ay_c = 2 * omega * ((vz * cos(L) * cos(AZ)) + vx_w * cos(L) * sin(AZ))
az_c = -2 * omega * ((vy * cos(L) * cos(AZ)) - vx_w * sin(L))
Mach = v/vs
""" initializing variables for plots"""
t_list = [t]
x_list = [x]
y_list = [y]
vy_list = [vy]
v_list = [v]
phi0_list = [phi0]
Mach_list = [Mach]
while y >= 0:
phi0 = phi0
"""drag calculation with variable density, Temp and sound speed"""
rho = rho0 * ((Tb / (Tb + Lb * (y - y0))) ** (1 + (g * M / (R *Lb))))
vs = 20.05 * np.sqrt(Tb + Lb * (y - y0)) # m/s speed of sound as a function of temperature
Cd3 = K3 / sqrt(v / vs)
Mach = v/vs
"""Determining drag regime"""
if v > 1.2 * vs: #supersonic
Cd = Cd3
elif v < 0.8 * vs: #subsonic
Cd = Cd1
else: #transonic
Cd = ((Cd3 - Cd1)*(v/vs - 0.8)/(0.4)) + Cd1
"""Acceleration due to Coriolis"""
ax_c = -2*omega*((vz_w*sin(L))+ vy*cos(L)*sin(AZ))
ay_c = 2*omega*((vz_w*cos(L)*cos(AZ))+ vx_w*cos(L)*sin(AZ))
az_c = -2*omega*((vy*cos(L)*cos(AZ))- vx_w*sin(L))
"""Total acceleration calcs"""
if vx > 0:
ax = -0.5*rho*((vx-wx)**2)*Cd*Area/m + ax_c
else:
ax = 0
""" Vy before and after peak"""
if vy > 0:
ay = (-0.5 * rho * (vy ** 2) * Cd * Area / m) - g + ay_c
else:
ay = (0.5 * rho * (vy ** 2) * Cd * Area / m) - g + ay_c
az = az_c
vx = vx + ax*dt # vx without wind
# vx_w = vx with drag and no wind + wind
vx_w = vx + 2*wx*(1-(vx/v0*np.cos(radians(phi0))))
vy = vy + ay*dt
vz = vz + az*dt
vz_w = vz + wz*(1-(vx/v0*np.cos(radians(phi0))))
"""projectile velocity"""
v = sqrt(vx_w**2 + vy**2 + vz**2)
"""new x, y, z positions"""
x = x + vx_w*dt
y = y + vy*dt
z = z + vz_w*dt
if y_max <= y:
y_max = y
phi_impact = degrees(atan(vy/vx)) #impact angle in degrees
""" appends selected data for ability to plot"""
t_list.append(t)
x_list.append(x)
y_list.append(y)
vy_list.append(vy)
v_list.append(v)
phi0_list.append(phi0)
Mach_list.append(Mach)
if y < 0:
break
t += dt
"""Range table output"""
table[i] = ('%.f' % phi0, '%.3f' % phi_impact, '%.1f' % x,'%.2f' % z, '%.1f' % y_max, '%.1f' % vx_w,'%.1f' % vz,'%.1f' % vy,'%.1f' % v,'%.2f' %Mach, '%.1f' % t)
""" Plot"""
plt.plot(x_list, y_list, label='%d°' % phi0)#plt.plot(x_list, y_list, label='%d°' % phi0)
plt.title('Altitude versus Range')
plt.ylabel('Altitude (m)')
plt.xlabel('Range (m)')
plt.axis([0, 30000, 0, 15000])
plt.grid(True)
print(table)
legend = plt.legend(title="Firing Angle",loc=0, fontsize='small', fancybox=True)
plt.show()
Thank you in advance
Which Editor Should I Use?
Personally, I prefer VSCode, but Sublime is also pretty popular. If you really want to go barebones, try Vim. All three are completely free.
Code Errors
After scanning your code snippet, it appears that you are caught in an infinite loop, which you enter with the statement while y >= 0. The reason you always get line 103 when you hit Ctrl+C is likely because that takes the longest, making it more likely to land there at any given time.
Note that currently, you can only escape your while loop through this branch:
if y_max <= y:
y_max= y
phi_impact = degrees(atan(vy/vx)) #impact angle in degrees
""" appends selected data for ability to plot"""
t_list.append(t)
x_list.append(x)
y_list.append(y)
vy_list.append(vy)
v_list.append(v)
phi0_list.append(phi0)
Mach_list.append(Mach)
if y < 0:
break
t += dt
This means that if ymax never drops below y, or y never drops below zero, then you will infinitely loop. Granted, I haven't looked at your code in any great depth, but from the surface it appears that y_max is never decremented (meaning it will always be at least equal to y). Furthermore, y is only updated when you do y = y + vy*dt, which will only ever increase y if vy >= 0 (I assume dt is always positive).
Debugging
As #Giacomo Catenazzi suggested, try printing out y and y_max at the top of the while loop and see how they change as your code runs. I suspect they are not decrementing like you expected.
This question already has answers here:
How to convert a decimal number into fraction?
(6 answers)
Is there a way to return a fully reduced ratio when calling .as_integer_ratio()?
(2 answers)
Is there an alternative to the: as_integer_ratio(), for getting "cleaner" fractions?
(2 answers)
Closed 1 year ago.
QUESTION:
I would like to convert floats into a ratio of integers in simplest form. (Not a duplicate of this question, see "EDIT" below). For example, 0.1 = 1, 10, 0.66666... = 2, 3, etc. In the code snippet below, I try doing this for x = 0.1, 0.2, ..., 1.0 using this default function; the method only works successfully for x = 0.5 and x = 1.0. Why does this algorithm fail for other values of x and what is a better method to do this? In case it is relevant, my use-case will be for dx ~ 0.0005 = x[1] - x[0] for 0.0005 < x 10.0.
CODE:
import numpy as np
f = np.vectorize(lambda x : x.as_integer_ratio())
x = np.arange(0.1, 1.1, 0.1)
nums, dens = f(x)
for xi, numerator, denominator in zip(x, nums, dens):
print("\n .. {} = {} / {}\n".format(xi, numerator, denominator))
OUTPUT:
.. 0.1 = 3602879701896397 / 36028797018963968
.. 0.2 = 3602879701896397 / 18014398509481984
.. 0.30000000000000004 = 1351079888211149 / 4503599627370496
.. 0.4 = 3602879701896397 / 9007199254740992
.. 0.5 = 1 / 2
.. 0.6 = 5404319552844595 / 9007199254740992
.. 0.7000000000000001 = 6305039478318695 / 9007199254740992
.. 0.8 = 3602879701896397 / 4503599627370496
.. 0.9 = 8106479329266893 / 9007199254740992
.. 1.0 = 1 / 1
EDIT:
This is not really a duplicate. Both methods of the accepted answer in the original question fail a basic use-case from my MWE. To show that the Fraction module gives the same error:
import numpy as np
from fractions import Fraction
f = np.vectorize(lambda x : Fraction(x))
x = np.arange(0.1, 1.1, 0.1)
y = f(x)
print(y)
## OUTPUT
[Fraction(3602879701896397, 36028797018963968)
Fraction(3602879701896397, 18014398509481984)
Fraction(1351079888211149, 4503599627370496)
Fraction(3602879701896397, 9007199254740992) Fraction(1, 2)
Fraction(5404319552844595, 9007199254740992)
Fraction(6305039478318695, 9007199254740992)
Fraction(3602879701896397, 4503599627370496)
Fraction(8106479329266893, 9007199254740992) Fraction(1, 1)]
I am trying to generate a list of values, and then plot those list of values using the MatPlotLib Hist function. This is what my graph looks like this: https://i.stack.imgur.com/u7P8Q.png
I've followed this process for two other graphs with no trouble at all, for some reason this one is giving me trouble.
This is my code:
for y in range(Nloop):
e0_y = e_List[y] # Takes the a value from these list and sets it equal to this variable
a0_y = a_List[y] # Same thing ^^^
Term_1 = (a0_y ** 4)/((m_tot**3)*eta)
Term_2 = (1 - e0_y**2)**(7/2)
Unit_Conversions = (c**5/G**3)
tau = (3/85) * Term_1 * Term_2 * Unit_Conversions
T_List[y] = tau
MIN, MAX = 1, 1e12
Nbins = 25
bins = 10 ** np.linspace(np.log10(MIN), np.log10(MAX), Nbins)
plt.hist(T_List, bins=25, histtype='step')
plt.xscale('log') # x-axis now has a log-scale
plt.yscale('log')
plt.title('Distribution')
plt.xlabel('T [sec]')
plt.ylabel('Frequency')
plt.show()
I'm working on some code which needs to be able to preform a 2d gaussian fitting. I mostly based my code on following question: Fitting a 2D Gaussian function using scipy.optimize.curve_fit - ValueError and minpack.error . Now is problem that I don't really have an initial guess about the different parameters that need to be used.
I've tried this:
def twoD_Gaussian(x_data_tuple, amplitude, xo, yo, sigma_x, sigma_y, theta, offset):
(x,y) = x_data_tuple
xo = float(xo)
yo = float(yo)
a = (np.cos(theta)**2)/(2*sigma_x**2) + (np.sin(theta)**2)/(2*sigma_y**2)
b = -(np.sin(2*theta))/(4*sigma_x**2) + (np.sin(2*theta))/(4*sigma_y**2)
c = (np.sin(theta)**2)/(2*sigma_x**2) + (np.cos(theta)**2)/(2*sigma_y**2)
g = offset + amplitude*np.exp( - (a*((x-xo)**2) + 2*b*(x-xo)*(y-yo)
+ c*((y-yo)**2)))
return g.ravel()
The data.reshape(201,201) is just something I took from the aformentioned question.
mean_gauss_x = sum(x * data.reshape(201,201)) / sum(data.reshape(201,201))
sigma_gauss_x = np.sqrt(sum(data.reshape(201,201) * (x - mean_gauss_x)**2) / sum(data.reshape(201,201)))
mean_gauss_y = sum(y * data.reshape(201,201)) / sum(data.reshape(201,201))
sigma_gauss_y = np.sqrt(sum(data.reshape(201,201) * (y - mean_gauss_y)**2) / sum(data.reshape(201,201)))
initial_guess = (np.max(data), mean_gauss_x, mean_gauss_y, sigma_gauss_x, sigma_gauss_y,0,10)
popt, pcov = curve_fit(twoD_Gaussian, (x, y), data, p0=initial_guess)
data_fitted = twoD_Gaussian((x, y), *popt)
If I try this, I get following error message: ValueError: setting an array element with a sequence.
Is the reasoning about the begin parameters correct?
And why do I get this error?
If I use the runnable code from the linked question and substitute your definition of initial_guess:
mean_gauss_x = sum(x * data.reshape(201,201)) / sum(data.reshape(201,201))
sigma_gauss_x = np.sqrt(sum(data.reshape(201,201) * (x - mean_gauss_x)**2) / sum(data.reshape(201,201)))
mean_gauss_y = sum(y * data.reshape(201,201)) / sum(data.reshape(201,201))
sigma_gauss_y = np.sqrt(sum(data.reshape(201,201) * (y - mean_gauss_y)**2) / sum(data.reshape(201,201)))
initial_guess = (np.max(data), mean_gauss_x, mean_gauss_y, sigma_gauss_x, sigma_gauss_y,0,10)
Then
print(inital_guess)
yields
(13.0, array([...]), array([...]), array([...]), array([...]), 0, 10)
Notice that some of the values in initial_guess are arrays. The optimize.curve_fit function expects initial_guess to be a tuple of scalars. This is the source of the problem.
The error message
ValueError: setting an array element with a sequence
often arises when an array-like is supplied when a scalar value is expected. It is a hint that the source of the problem may have to do with an array having the wrong number of dimensions. For example, it might arise if you pass a 1D array to a function that expects a scalar.
Let's look at this piece of code taken from the linked question:
x = np.linspace(0, 200, 201)
y = np.linspace(0, 200, 201)
X, Y = np.meshgrid(x, y)
x and y are 1D arrays, while X and Y are 2D arrays. (I've capitalized all 2D arrays to help distinguish them from 1D arrays).
Now notice that Python sum and NumPy's sum method behave differently when applied to 2D arrays:
In [146]: sum(X)
Out[146]:
array([ 0., 201., 402., 603., 804., 1005., 1206., 1407.,
1608., 1809., 2010., 2211., 2412., 2613., 2814., 3015.,
...
38592., 38793., 38994., 39195., 39396., 39597., 39798., 39999.,
40200.])
In [147]: X.sum()
Out[147]: 4040100.0
The Python sum function is equivalent to
total = 0
for item in X:
total += item
Since X is a 2D array, the loop for item in X is iterating over the rows of X. Each item is therefore a 1D array representing a row of X. Thus, total ends up being a 1D array.
In contrast, X.sum() sums all the elements in X and returns a scalar.
Since initial_guess should be a tuple of scalars,
everywhere you use sum you should instead use the NumPy sum method. For example, replace
mean_gauss_x = sum(x * data) / sum(data)
with
mean_gauss_x = (X * DATA).sum() / (DATA.sum())
import numpy as np
import scipy.optimize as optimize
import matplotlib.pyplot as plt
# define model function and pass independant variables x and y as a list
def twoD_Gaussian(data, amplitude, xo, yo, sigma_x, sigma_y, theta, offset):
X, Y = data
xo = float(xo)
yo = float(yo)
a = (np.cos(theta) ** 2) / (2 * sigma_x ** 2) + (np.sin(theta) ** 2) / (
2 * sigma_y ** 2
)
b = -(np.sin(2 * theta)) / (4 * sigma_x ** 2) + (np.sin(2 * theta)) / (
4 * sigma_y ** 2
)
c = (np.sin(theta) ** 2) / (2 * sigma_x ** 2) + (np.cos(theta) ** 2) / (
2 * sigma_y ** 2
)
g = offset + amplitude * np.exp(
-(a * ((X - xo) ** 2) + 2 * b * (X - xo) * (Y - yo) + c * ((Y - yo) ** 2))
)
return g.ravel()
# Create x and y indices
x = np.linspace(0, 200, 201)
y = np.linspace(0, 200, 201)
X, Y = np.meshgrid(x, y)
# create data
data = twoD_Gaussian((X, Y), 3, 100, 100, 20, 40, 0, 10)
data_noisy = data + 0.2 * np.random.normal(size=data.shape)
DATA = data.reshape(201, 201)
# add some noise to the data and try to fit the data generated beforehand
mean_gauss_x = (X * DATA).sum() / (DATA.sum())
sigma_gauss_x = np.sqrt((DATA * (X - mean_gauss_x) ** 2).sum() / (DATA.sum()))
mean_gauss_y = (Y * DATA).sum() / (DATA.sum())
sigma_gauss_y = np.sqrt((DATA * (Y - mean_gauss_y) ** 2).sum() / (DATA.sum()))
initial_guess = (
np.max(data),
mean_gauss_x,
mean_gauss_y,
sigma_gauss_x,
sigma_gauss_y,
0,
10,
)
print(initial_guess)
# (13.0, 100.00000000000001, 100.00000000000001, 57.106515650488404, 57.43620227324201, 0, 10)
# initial_guess = (3,100,100,20,40,0,10)
popt, pcov = optimize.curve_fit(twoD_Gaussian, (X, Y), data_noisy, p0=initial_guess)
data_fitted = twoD_Gaussian((X, Y), *popt)
fig, ax = plt.subplots(1, 1)
ax.imshow(
data_noisy.reshape(201, 201),
cmap=plt.cm.jet,
origin="bottom",
extent=(X.min(), X.max(), Y.min(), Y.max()),
)
ax.contour(X, Y, data_fitted.reshape(201, 201), 8, colors="w")
plt.show()
I converted a Matlab code into python by manually typing it out. However i keep getting an error message which i still have not been able to fix. what am i doing wrong and how do i get the plot as that in Matlab? Just is little information about the code; this is a Explicit finite difference method for solving pressure distribution in an oil reservoir with production from the middle block only. Its similar to the heat equation, Ut=Uxx. I was told to add more text because my question is mostly code so had to add all these details. I think that notification has vanished now.
[P_new[N] = 4000 #last blocks at all time levels equals 4000
IndexError: index 9 is out of bounds for axis 0 with size 9]
The Matlab code which runs ok is below: The python code follows.
clear
clc
% Solution of P_t = P_{xx}
L = 1000 ; %ft length of reservoir
W = 100 ; %ft reservoir width
h = 50 ;%ft pay thickness
poro = 0.25; % rock porosity
k_o = 5; %md effective perm to oil
P_i = 4000; %psia initial pressure
B_o = 1.25; %oil formation vol fact
mu = 5; %cp oil visc
c_t = 0.0000125; %1/atm total compressibility
Q_o = 10;%stb/day production rate from central well
alpha = c_t*mu*poro/k_o;
T = 1;
N_time = 50;
dt = T/N_time;
% % Number of grid cells
N =9; %number of grid cells
%N =11;%number of grid cells
dx = (L/(N-1)); %distance between grid blocks
x = 0+dx*0.5:dx:L+dx; %points in space
for i=1:N
P_old(i)=P_i;
FPT(i)=0;
end
FPT((N+1)/2)=-Q_o*B_o*mu/1.127/W/dx/h/k_o; %source term at the center block of grid cell
P_new = P_old;
for j = 1:N_time
for k = 1: N
if k<2
P_new(k)=4000;%P_old(k)+dt/alpha*((P_old(k+1)-2*P_old(k)+P_old(k))/dx^2+FPT(k));
elseif k > N-1
P_new(k) = 4000;%P_old(k)+dt/alpha*((P_old(k)-2*P_old(k)+P_old(k-1))/dx^2+FPT(k));
else
P_new(k) = P_old(k)+dt/alpha*((P_old(k+1)-2*P_old(k)+P_old(k-1))/dx^2+FPT(k));
end
end
plot(x,P_new, '-x')
xlabel('X')
ylabel('P(X)')
hold on
grid on
%%update "u_old" before you move forward to the next time level
P_old = P_new;
end
hold off
Python Code:
import numpy as np
import matplotlib.pyplot as plt
# Solution of P_t = P_{xx}
L = 1000 #ft length of reservoir
W = 100 #ft reservoir width
h = 50 #ft pay thickness
poro = 0.25 # rock porosity
k_o = 5 #md effective perm to oil
P_i = 4000 #psia initial pressure
B_o = 1.25 #oil formation vol fact
mu = 5 #cp oil visc
c_t = 0.0000125 #1/atm total compressibility
Q_o = 10 #stb/day production rate from central well
alpha = c_t * mu * poro / k_o
T = 1
N_time = 20
dt = T / N_time
# % Number of grid cells
N = 9 #number of grid cells
dx = (L / (N - 1)) #distance between grid blocks
x= np.arange(0.0,L+dx,dx)
P_old = np.zeros_like(x) #pressure at previous time level
P_new = np.zeros_like(x) #pressure at previous time level
FPT = np.zeros_like(x)
for i in range(0,N):
P_old[i]= P_i
FPT[int((N + 1) / 2)]= -Q_o * B_o * mu / (1.127 * W * dx * h * k_o) # source term at the center block of grid cell
P_new = P_old
d=np.arange(0,N)
for j in range(0,N_time):
for k in range(0,N):
P_new[0] = 4000 #pressure at first block for all time levels equals 4000
P_new[N] = 4000 #pressure at last block for all time levels equals 4000
P_new[k]= P_old[k] + dt / alpha * ((P_old[k+1] - 2 * P_old[k] + P_old[k - 1]) / dx ** 2 + FPT[k])
plt.plot(x, P_new)
plt.xlabel('X')
plt.ylabel('P(X)')
P_old = P_new
Matlab uses 1 based indexing , Python arrays use "0" based indexing. If you define an array of length N in python, the indices are from 0 to N-1.
So just replace the index N to index N-1 in your code as below and it works.
import numpy as np
import matplotlib.pyplot as plt
# Solution of P_t = P_{xx}
L = 1000 #ft length of reservoir
W = 100 #ft reservoir width
h = 50 #ft pay thickness
poro = 0.25 # rock porosity
k_o = 5 #md effective perm to oil
P_i = 4000 #psia initial pressure
B_o = 1.25 #oil formation vol fact
mu = 5 #cp oil visc
c_t = 0.0000125 #1/atm total compressibility
Q_o = 10 #stb/day production rate from central well
alpha = c_t * mu * poro / k_o
T = 1
N_time = 20
dt = T / N_time
# % Number of grid cells
N = 9 #number of grid cells
dx = (L / (N - 1)) #distance between grid blocks
x= np.arange(0.0,L+dx,dx)
P_old = np.zeros_like(x) #pressure at previous time level
P_new = np.zeros_like(x) #pressure at previous time level
FPT = np.zeros_like(x)
for i in range(0,N):
P_old[i]= P_i
FPT[int((N + 1) / 2)]= -Q_o * B_o * mu / (1.127 * W * dx * h * k_o) # source term at the center block of grid cell
P_new = P_old
d=np.arange(0,N)
for j in range(0,N_time):
for k in range(0,N-1):
P_new[0] = 4000 #pressure at first block for all time levels equals 4000
P_new[N-1] = 4000 #pressure at last block for all time levels equals 4000
P_new[k]= P_old[k] + dt / alpha * ((P_old[k+1] - 2 * P_old[k] + P_old[k - 1]) / dx ** 2 + FPT[k])
plt.plot(x, P_new)
plt.xlabel('X')
plt.ylabel('P(X)')
P_old = P_new
output: