Any suggestions to make python code faster? - python-3.x

My present code takes too much time to execute say N=100000 values. Last time I tried it took around 4 hrs. Which is too much computing time. If someone can suggest anything to make the code a little faster?
def gen_chain(N):
coordinates = np.loadtxt('saw.txt', skiprows=0)
return coordinates
def lj(rij2):
sig_by_r6 = np.power(sigma / rij2, 3)
sig_by_r12 = np.power(sig_by_r6, 2)
lje = 4.0 * epsilon * (sig_by_r12 - sig_by_r6)
return lje
def fene(rij2):
return (-0.5 * K * R**2 * np.log(1 - ((np.sqrt(rij2) - r0)**2 / R**2)))
def total_energy(coord):
# Non-bonded
e_nb = 0
for i in range(N):
for j in range(i - 1):
ri = coord[i]
rj = coord[j]
rij = ri - rj
rij2 = np.dot(rij, rij)
if (np.sqrt(rij2) < rcutoff):
e_nb += lj(rij2)
# Bonded
e_bond = 0
for i in range(1, N):
ri = coord[i]
rj = coord[i - 1]
rij = ri - rj
rij2 = np.dot(rij, rij)
e_bond += fene(rij2)
return e_nb + e_bond
def move(coord):
trial = np.ndarray.copy(coord)
for i in range(N):
delta = (2.0 * np.random.rand(3) - 1) * max_delta
trial[i] += delta
return trial
def accept(delta_e):
beta = 1.0 / T
if delta_e <= 0.0:
return True
random_number = np.random.rand(1)
p_acc = np.exp(-beta * delta_e)
if random_number < p_acc:
return True
return False
if __name__ == "__main__":
# FENE parameters
K = 40
R = 0.3
r0 = 0.7
# LJ parameters
sigma = 0.624
epsilon = 1.0
# MC parameters
N = 100 # number of particles
rcutoff = 2.5 * sigma
max_delta = 0.01
n_steps = 100000
T = 0.5
coord = gen_chain(N)
energy_current = total_energy(coord)
traj = open('traj.xyz', 'w')
for step in range(n_steps):
if step % 1000 == 0:
traj.write(str(N) + '\n\n')
for i in range(N):
traj.write("C %10.5f %10.5f %10.5f\n" % (coord[i][0], coord[i][1], coord[i][2]))
print(step, energy_current)
coord_trial = move(coord)
energy_trial = total_energy(coord_trial)
delta_e = energy_trial - energy_current
if accept(delta_e):
coord = coord_trial
energy_current = energy_trial
traj.close()
I know it cannot be compared to C/C++.Therefore, please don't suggest to use any other language. I also welcome suggestions regarding some unnecessary objects.

Related

'>=' not supported between instances of 'list' and 'float' for numpy where

I am new to coding and I'm working on my college project on which I need to make a bio-inspired algorithm teacher learning-based Algorithm, but here is some error is coming
here is my tlbo code
class Student:
def __init__(self, fitness, dim, minx, maxx, seed):
self.rnd = random.Random(seed)
# a list of size dim
# with 0.0 as value of all the elements
self.position = [0.0 for i in range(dim)]
# loop dim times and randomly select value of decision var
# value should be in between minx and maxx
for i in range(dim):
self.position[i] = ((maxx - minx) *
self.rnd.random() + minx)
# compute the fitness of student
self.fitness = fitness(self.position)
def tlbo(fitness, max_iter, n, dim, minx, maxx):
rnd = random.Random(0)
# create n random students
classroom = [Student(fitness, dim, minx, maxx, i) for i in range(n)]
# compute the value of best_position and best_fitness in the classroom
Xbest = [0.0 for i in range(dim)]
Fbest = sys.float_info.max
for i in range(n): # check each Student
if classroom[i].fitness < Fbest:
Fbest = classroom[i].fitness
Xbest = copy.copy(classroom[i].position)
# convergence graph
convergence1 = []
timerStart = time.time()
# main loop of tlbo
Iter = 0
while Iter < max_iter:
# after every 10 iterations
# print iteration number and best fitness value so far
if Iter % 10 == 0 and Iter > 1:
print("Iter = " + str(Iter) + " best fitness = %.3f" % Fbest)
if Iter % 1 ==0 :
convergence1.append(Fbest)
# for each student of classroom
for i in range(n):
### Teaching phase of ith student
# compute the mean of all the students in the class
Xmean = [0.0 for i in range(dim)]
for k in range(n):
for j in range(dim):
Xmean[j] += classroom[k].position[j]
for j in range(dim):
Xmean[j] /= n;
# initialize new solution
Xnew = [0.0 for i in range(dim)]
# teaching factor (TF)
# either 1 or 2 ( randomly chosen)
TF = random.randint(1, 3)
# best student of the class is teacher
Xteacher = Xbest
# compute new solution
for j in range(dim):
Xnew[j] = classroom[i].position[j] + rnd.random() * (Xteacher[j] - TF * Xmean[j])
# if Xnew < minx OR Xnew > maxx
# then clip it
for j in range(dim):
Xnew[j] = max(Xnew[j], minx)
Xnew[j] = min(Xnew[j], maxx)
# compute fitness of new solution
fnew = fitness(Xnew)
# if new solution is better than old
# replace old with new solution
if (fnew < classroom[i].fitness):
classroom[i].position = Xnew
classroom[i].fitness = fnew
# update best student
if (fnew < Fbest):
Fbest = fnew
Xbest = Xnew
### learning phase of ith student
# randomly choose a solution from classroom
# chosen solution should not be ith student
p = random.randint(0, n - 1)
while (p == i):
p = random.randint(0, n - 1)
# partner solution
Xpartner = classroom[p]
Xnew = [0.0 for i in range(dim)]
if (classroom[i].fitness < Xpartner.fitness):
for j in range(dim):
Xnew[j] = classroom[i].position[j] + rnd.random() * (
classroom[i].position[j] - Xpartner.position[j])
else:
for j in range(dim):
Xnew[j] = classroom[i].position[j] - rnd.random() * (
classroom[i].position[j] - Xpartner.position[j])
# if Xnew < minx OR Xnew > maxx
# then clip it
for j in range(dim):
Xnew[j] = max(Xnew[j], minx)
Xnew[j] = min(Xnew[j], maxx)
# compute fitness of new solution
fnew = fitness(Xnew)
# if new solution is better than old
# replace old with new solution
if (fnew < classroom[i].fitness):
classroom[i].position = Xnew
classroom[i].fitness = fnew
# update best student
if (fnew < Fbest):
Fbest = fnew
Xbest = Xnew
Iter += 1
# end-while
timerEnd = time.time()
print(timerEnd-timerStart)
y = np.array(convergence1, dtype=np.longdouble)
x = np.arange(0, max_iter, dtype=int) + 1
print(x)
print(y)
timerEnd = time.time()
print('Completed in', (timerEnd - timerStart))
fire = round((timerEnd - timerStart), 2)
plt.plot(x, y, 'o-')
plt.xlabel("Iterations")
plt.ylabel("Fitness")
plt.title(
f"Convergence_curve for CSO for parameter including population "
f"{n}, \niteration {max_iter},and max fitness is:{round(min(convergence1), 3)}")
plt.show()
opts = {"p": Xbest, 'c': round(min(convergence1), 3), "ti": fire}
return opts
and here is my fitness function
def fitness_function(positions):
print(positions)
features = np.where(positions >= 0.4999)[0]
# print('selected_features:', features)
# print(train_df.head())
train_xf = train_x.iloc[:, features]
test_xf = test_x.iloc[:, features]
knn_classifier = Pipeline([('s', StandardScaler()), ('t', MinMaxScaler()),
('m', RandomForestClassifier(n_estimators=100, n_jobs=14))])
knn_classifier.fit(train_xf, train_y)
accuracy = knn_classifier.score(test_xf, test_y)
# print('Accuracy:', accuracy)
w = 0.9
return -(w * accuracy + (1 - w) * 1 / (len(features)))
here the main problem which is coming is ,
Traceback (most recent call last):
self.fitness = fitness(self.position)
features = np.where(positions >= 0.4999)[0]
TypeError: '>' not supported between instances of 'list' and 'float'
the main problem is my tlbo code is generating values for the best-fit position [0.456621, -0.616164564] and I need to convert it to [1,2] so that I can run knn and get accuracy result and RUC curve, so what I should do now?
Replace the line with features = np.where(np.array(positions) >= 0.4999)[0]

Particle Collision Simulation Python

I'm trying to create a relatively simple particle simulation, which should account for gravity, drag, the collision with other particles (inelastic collision) and the collision with walls (perfectly elastic). I got the gravity and drag part working with the velocity Verlet algorithm but its as of right now not capable of setting the particles to an equilibrium state. Furthermore if I add multiple particles they sometimes climb on each other which is due (as I believe) to them still having very small velocity components which asymptotically drives to zero. I tried to cut off the velocity of the particles if the energy of a particle gets sufficiently small but it wouldn't look realistic. Could somebody maybe point out some advice how to fix these issues. I got a particle Object:
import pygame
import random
import numpy as np
import operator
from itertools import combinations
class Particle:
def __init__(self):
self.mass = 10
self.radius = random.randint(10, 50)
self.width, self.height = 700, 500
self.pos = np.array((self.width/2, self.height/2))
self.v = np.array((0.0, 0.0))
self.acc = np.array((0.0, 0.0))
self.bounce = 0.95
I use the Verlet-Integration to account for gravity and drag forces:
def update(self, ball, dt):
new_pos = np.array((ball.pos[0] + ball.v[0]*dt + ball.acc[0]*(dt*dt*0.5), ball.pos[1] + ball.v[1]*dt + ball.acc[1]*(dt*dt*0.5)))
new_acc = np.array((self.apply_forces(ball))) # only needed if acceleration is not constant
new_v = np.array((ball.v[0] + (ball.acc[0]+new_acc[0])*(dt*0.5), ball.v[1] + (ball.acc[1]+new_acc[1])*(dt*0.5)))
ball.pos = new_pos;
ball.v = new_v;
ball.acc = new_acc;
def apply_forces(self, ball):
grav_acc = [0.0, 9.81]
drag_force = [0.5 * self.drag * (ball.v[0] * abs(ball.v[0])), 0.5 * self.drag * (ball.v[1] * abs(ball.v[1]))] #D = 0.5 * (rho * C * Area * vel^2)
drag_acc = [drag_force[0] / ball.mass, drag_force[1] / ball.mass] # a = F/m
return (-drag_acc[0]),(grav_acc[1] - drag_acc[1])
And here I calculate the collision part:
def collision(self):
pairs = combinations(range(len(self.ball_list)), 2)
for i,j in pairs:
part1 = self.ball_list[i]
part2 = self.ball_list[j]
distance = list(map(operator.sub, self.ball_list[i].pos, self.ball_list[j].pos))
if np.hypot(*distance) < self.ball_list[i].radius + self.ball_list[j].radius:
distance = part1.pos - part2.pos
rad = part1.radius + part2.radius
slength = (part1.pos[0] - part2.pos[0])**2 + (part1.pos[1] - part2.pos[1])**2
length = np.hypot(*distance)
factor = (length-rad)/length;
x = part1.pos[0] - part2.pos[0]
y = part1.pos[1] - part2.pos[1]
part1.pos[0] -= x*factor*0.5
part1.pos[1] -= y*factor*0.5
part2.pos[0] += x*factor*0.5
part2.pos[1] += y*factor*0.5
u1 = (part1.bounce*(x*part1.v[0]+y*part1.v[1]))/slength
u2 = (part2.bounce*(x*part2.v[0]+y*part2.v[1]))/slength
part1.v[0] = u2*x-u1*x
part1.v[1] = u1*x-u2*x
part2.v[0] = u2*y-u1*y
part2.v[1] = u1*y-u2*y
def check_boundaries(self, ball):
if ball.pos[0] + ball.radius > self.width:
ball.v[0] *= -ball.bounce
ball.pos[0] = self.width - ball.radius
if ball.pos[0] < ball.radius:
ball.v[0] *= -ball.bounce
ball.pos[0] = ball.radius
if ball.pos[1] + ball.radius > self.height:
self.friction = True
ball.v[1] *= -ball.bounce
ball.pos[1] = self.height - ball.radius
elif ball.pos[1] < ball.radius:
ball.v[1] *= -ball.bounce
ball.pos[1] = ball.radius

Scipy optimize.minimize with multi- parameters

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from scipy import linalg, optimize
%matplotlib inline
Data load
data = pd.read_csv("D:/Stat/TimeSeries/KRW_month_0617_1.csv",index_col="Date") / 100
para = open("D:/Stat/TimeSeries/KRW_month_0617_1.txt").readlines()[0:2]
data.index = pd.to_datetime(data.index)
Parameters
cond = []
params = []
time = []
for i in para:
j = i.split()
for k in j:
cond.append(k)
cond = cond[1:]
for i in range(len(cond)):
cond[i] = round(float(cond[i]),4)
params = cond[0:23]
time = cond[23:]
maturity = np.array(time[1:])
timegap = 1/cond[23]
Functions We need
def Paramcheck(Params, checkStationary = 1):
result = 0
Kappa = np.array([[params[20],0,0], [0,params[21],0], [0,0,params[22]]])
Sigma = np.array([[params[1],0,0], [params[2],params[3],0], [params[4],params[5],params[6]]])
State = np.array([params[7], params[8], params[9]])
Lambda = params[0]
SigmaEps = np.identity(10)
for i in range(10):
SigmaEps[i][i] = params[i+10]
for i in range(len(Sigma)):
if Sigma[i][i] < 0:
result = 1
for j in SigmaEps:
if np.any(SigmaEps) < 0:
result = 1
if Lambda < 0.05 or Lambda > 2:
result = 1
elif State[0] < 0:
result = 1
elif Kappa[0][0] < 0:
result = 1
if result == 0 and checkStationary > 0:
if max(np.linalg.eigvals(-Kappa).real) > 0:
result = 2
return result
def CheckDet(x):
if x == np.inf or x == np.nan:
result = 1
elif x < 0:
result = 2
elif abs(x) < 10**-250:
result = 3
else:
result = 0
return result
def NS_factor(lambda_val, maturity):
col1 = np.ones(len(maturity))
col2 = (1 - np.exp(-lambda_val*maturity))/(lambda_val*maturity)
col3 = col2 - np.exp(-lambda_val*maturity)
factor = np.array([col1,col2,col3]).transpose()
return factor
def DNS_Kalman_filter(Params, *args):
N = Paramcheck(Params)
if N == 0:
Kappa = np.array([[params[20],0,0], [0,params[21],0], [0,0,params[22]]])
Sigma = np.array([[params[1],0,0], [params[2],params[3],0],
[params[4],params[5],params[6]]])
State = np.array([params[7], params[8], params[9]])
Lambda = params[0]
SigmaEps = np.identity(10)
for i in range(10):
SigmaEps[i][i] = params[i+10]
Obs_Yield = args[0]
Obs_Date = args[1]
Timegap = args[2]
Obs_Mty = args[3]
Finalstate = args[4]
Mty_length = len(Obs_Mty)
B = NS_factor(lambda_val = Lambda,maturity = Obs_Mty)
H_large = SigmaEps **2
N_obs = len(Obs_Date)
LLH_vec = np.zeros(N_obs)
phi1 = linalg.expm(-Kappa*Timegap)
phi0 = (np.identity(3)-phi1) # State
Eigenvalues = np.linalg.eig(Kappa)[0]
Eigen_vec = np.linalg.eig(Kappa)[1]
Eigen_vec_inv = np.linalg.inv(Eigen_vec)
S = Eigen_vec_inv # Sigma # Sigma.transpose() # Eigen_vec_inv.transpose()
Atilde = np.dot(Sigma[0], Sigma[0])
Btilde = np.dot(Sigma[1], Sigma[1])
Ctilde = np.dot(Sigma[2], Sigma[2])
Dtilde = np.dot(Sigma[0], Sigma[1])
Etilde = np.dot(Sigma[0], Sigma[2])
Ftilde = np.dot(Sigma[1], Sigma[2])
res1= Atilde* Obs_Mty* Obs_Mty/6
res2= Btilde*(1/(2*Lambda**2) - (1-np.exp(-Lambda*Obs_Mty))/(Lambda**3*Obs_Mty) + (1-
np.exp(-2*Lambda*Obs_Mty))/(4*Lambda**3*Obs_Mty))
res3= Ctilde*(1/(2*Lambda**2) + np.exp(-Lambda*Obs_Mty)/(Lambda**2)-
Obs_Mty*np.exp(-2*Lambda*Obs_Mty)/(4*Lambda) -
3*np.exp(-2*Lambda*Obs_Mty)/(4*Lambda**2) - 2*(1-np.exp(-
Lambda*Obs_Mty))/(Lambda**3*Obs_Mty) + 5*(1-
np.exp(-2*Lambda*Obs_Mty))/(8*Lambda**3*Obs_Mty))
res4= Dtilde*(Obs_Mty/(2*Lambda) + np.exp(-Lambda*Obs_Mty)/(Lambda**2) - (1-np.exp(-
Lambda*Obs_Mty))/(Lambda**3*Obs_Mty))
res5= Etilde*(3*np.exp(-Lambda*Obs_Mty)/(Lambda**2) + Obs_Mty/(2*Lambda)+Obs_Mty*np.exp(-
Lambda*Obs_Mty)/(Lambda) - 3*(1-np.exp(-Lambda*Obs_Mty))/(Lambda**3*Obs_Mty))
res6= Ftilde*(1/(Lambda**2) + np.exp(-Lambda*Obs_Mty)/(Lambda**2) -
np.exp(-2*Lambda*Obs_Mty)/(2*Lambda**2) - 3*(1-np.exp(-
Lambda*Obs_Mty))/(Lambda**3*Obs_Mty) + 3*(1-
np.exp(-2*Lambda*Obs_Mty))/(4*Lambda**3*Obs_Mty))
val = res1 + res2 + res3 + res4 + res5 + res6
V_mat = np.zeros([3,3])
V_lim = np.zeros([3,3])
for i in range(3):
for j in range(3):
V_mat[i][j] = S[i][j]*(1-np.exp(-(Eigenvalues[i] +
Eigenvalues[j])*Timegap))/(Eigenvalues[i] + Eigenvalues[j])
V_lim[i][j] = S[i][j]/(Eigenvalues[i] + Eigenvalues[j])
Q = (Eigen_vec # V_mat # Eigen_vec.transpose()).real
Sigma_lim = (Eigen_vec # V_lim # Eigen_vec.transpose()).real
for i in range(N_obs):
y = Obs_Yield[i]
xhat = phi0 + phi1 # State
y_implied = B # xhat
v = y - y_implied + val
Sigmahat = phi1 # Sigma_lim # phi1.transpose() + Q
F = B # Sigmahat # B.transpose() + H_large
detF = np.linalg.det(F)
if CheckDet(detF) > 0:
N = 3
break
Finv = np.linalg.inv(F)
State = xhat + Sigmahat # B.transpose() # Finv # v
Sigma_lim = Sigmahat - Sigmahat # B.transpose() # Finv # B # Sigmahat
LLH_vec[i] = np.log(detF) + v.transpose() # Finv # v
if N == 0:
if Finalstate:
yDate = Obs_Date[-1]
result = np.array([yDate,State])
else:
result = 0.5 * (sum(LLH_vec) + Mty_length*N_obs*np.log(2*np.pi))
else:
result = 7000000
return result
I made a code that does Arbitrage Free Nelson-Siegel model. Data is return rates of bond (1Y,1.5Y, ... ,20Y). I wanna optimize that function with scipy optimize.minimize function with fixed *args.
Suppose that Initial parmas are verified that it's close to optimized params from empirical experiments using Dynamic Nelson-Siegel Model.
LLC_new = 0
while True:
LLC_old = LLC_new
OPT = optimize.minimize(x0=params,fun=DNS_Kalman_filter, args=
(data.values,data.index,timegap,maturity,0))
params = OPT.x
LLC_new = round(OPT.fun,5)
print("Current LLC: %0.5f" %LLC_new)
if LLC_old == LLC_new:
OPT_para = params
FinalState = DNS_Kalman_filter(params,data.values,data.index,timegap,maturity,True)
break
Result is
Current LLC: -7613.70146
Current LLC: -7613.70146
LLC(log-likelihood value) isn't maximized. It's not a result I desire using Optimizer.
Is there any solution for that?
In R, there is optim() function works as similar as scipy.optimize.minimize() which works really well. I also have a R code for that very similar to this Python code.

Monte Carlo simulation of a system of polymer chain

I want to perform Monte Carlo simulation to the particles which are interacting via Lennard-Jones potential + FENE potential. I'm getting negative values in the FENE potential which have the log value in it. The error is "RuntimeWarning: invalid value encountered in log return (-0.5 * K * R**2 * np.log(1-((np.sqrt(rij2) - r0) / R)**2))" The FENE potential is given by:
import numpy as np
def gen_chain(N, R0):
x = np.linspace(1, (N-1)*0.8*R0, num=N)
y = np.zeros(N)
z = np.zeros(N)
return np.column_stack((x, y, z))
def lj(rij2):
sig_by_r6 = np.power(sigma/rij2, 3)
sig_by_r12 = np.power(sig_by_r6, 2)
lje = 4.0 * epsilon * (sig_by_r12 - sig_by_r6)
return lje
def fene(rij2):
return (-0.5 * K * R**2 * np.log(1-((np.sqrt(rij2) - r0) / R)**2))
def total_energy(coord):
# Non-bonded
e_nb = 0
for i in range(N):
for j in range(i-1):
ri = coord[i]
rj = coord[j]
rij = ri - rj
rij2 = np.dot(rij, rij)
if (np.sqrt(rij2) < rcutoff):
e_nb += lj(rij2)
# Bonded
e_bond = 0
for i in range(1, N):
ri = coord[i]
rj = coord[i-1]
rij = ri - rj
rij2 = np.dot(rij, rij)
e_bond += fene(rij2)
return e_nb + e_bond
def move(coord):
trial = np.ndarray.copy(coord)
for i in range(N):
delta = (2.0 * np.random.rand(3) - 1) * max_delta
trial[i] += delta
return trial
def accept(delta_e):
beta = 1.0/T
if delta_e <= 0.0:
return True
random_number = np.random.rand(1)
p_acc = np.exp(-beta*delta_e)
if random_number < p_acc:
return True
return False
if __name__ == "__main__":
# FENE parameters
K = 40
R = 0.3
r0 = 0.7
# LJ parameters
sigma = r0/0.33
epsilon = 1.0
# MC parameters
N = 50 # number of particles
rcutoff = 2.5*sigma
max_delta = 0.01
n_steps = 10000000
T = 0.5
coord = gen_chain(N, R)
energy_current = total_energy(coord)
traj = open('traj.xyz', 'w')
for step in range(n_steps):
if step % 1000 == 0:
traj.write(str(N) + '\n\n')
for i in range(N):
traj.write("C %10.5f %10.5f %10.5f\n" % (coord[i][0], coord[i][1], coord[i][2]))
print(step, energy_current)
coord_trial = move(coord)
energy_trial = total_energy(coord_trial)
delta_e = energy_trial - energy_current
if accept(delta_e):
coord = coord_trial
energy_current = energy_trial
traj.close()
The problem is that calculating rij2 = np.dot(rij, rij) in total energy with the constant values you use is always a very small number. Looking at the expression inside the log used to calculate FENE, np.log(1-((np.sqrt(rij2) - r0) / R)**2), I first noticed that you're taking the square root of rij2 which is not consistent with the formula you provided.
Secondly, notice that ((rij2 - r0) / R)**2 is the same as ((r0 - rij2) / R)**2, since the sign gets lost when squaring. Because rij2 is very small (already in the first iteration -- I checked by printing the values), this will be more or less equal to ((r0 - 0.05)/R)**2 which will be a number bigger than 1. Once you subtract this value from 1 in the log expression, 1-((np.sqrt(rij2) - r0) / R)**2 will be equal to np.nan (standing for "Not A Number"). This will propagate through all the function calls (for example, calling energy_trial = total_energy(coord_trial) will effectively set energy_trial to np.nan), until an error will be raised by some function.
Maybe you could do something with np.isnan() call, documented here. Moreover, you should check how you iterate through the coord (there's some inconsistencies throughout the code) -- I suggest you check the code review community as well.

How can I speed up this code, it has a very big input file

Could you please help me speed up this code?
It takes a very long time to run because of how big the input file is, thank you to anyone who helps out.
racers = [int(file[0].split()[0]) / float(x) for x in file[0].split()[1::]]
print("hi")
def av(race):
race = race.split()
j = 0
while j != len([float(race[0]) / float(x) for x in race[1::]]):
racers[j] = [float(race[0]) / float(x) for x in race[1::]][j] + racers[j]
j += 1
for i in range(1, len(file)):
av(file[i])
a = min(racers)
del(racers[racers.index(min(racers))])
b = min(racers)
c = b-a
h = int(c)
c-=h
m = int(c * 60)
c-=m/60
s = round(c * 60 * 60)
print(str(h) + "h" + str(m) + "m" + str(s) + "s")

Resources