+10 XP

For Loops in Python

A for loop repeats code for every value in a sequence. In neuroscience simulations, we loop through time: for each millisecond, update the neuron state.

range(n) generates numbers 0, 1, 2, …, n−1. Why n−1? Python starts counting at 0. range(5) gives [0, 1, 2, 3, 4] — that's 5 numbers total.

python
# Loop through time steps
dt = 1e-3
for step in range(5):
→ range(5) gives steps: 0, 1, 2, 3, 4
    t = step * dt  # convert step number to time in seconds
→ step * dt converts integer step → actual time in seconds
    print(f"Step {step}: t = {t*1000:.1f} ms")

In the NMA simulation we use range(int(t_max/dt)) to get all steps. With t_max = 150e-3 and dt = 1e-3, that's range(150) — 150 time steps covering 150 ms.

python
import numpy as np
t_max = 150e-3
dt = 1e-3
num_steps = int(t_max / dt)
print(f"Total steps: {num_steps}")
for step in range(3):  # show first 3 steps only
    t = step * dt
    print(f"  step={step}, t={t*1000:.0f} ms")

This pattern — range(int(t_max/dt)) — appears in every NMA time-series simulation.