# Questions about simulation.step()

**URL:** <https://pybamm.discourse.group/t/questions-about-simulation-step/146>\
**Category:** PyBaMM Q&A\
**Created:** [5 February 2025 22:53 UTC](https://pybamm.discourse.group/t/questions-about-simulation-step/146 "2025-02-05T22:53:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![appana.3](https://avatars.discourse-cdn.com/v4/letter/a/b782af/32.png) [@appana.3](https://pybamm.discourse.group/u/appana.3)\
**Post date:** [5 February 2025 22:53 UTC](https://pybamm.discourse.group/t/questions-about-simulation-step/146/1 "2025-02-05T22:53:00Z")

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Hi,

I want to run a custom current profile (let’s say [0, 0.5, 0.45, 0.47]) using sim.step instead of sim.solve. How do I do that?

Here’s a MWE of what I’m trying to achieve.

```python
# Using sim.solve()
import pybamm
import numpy as np

parameter_values = pybamm.ParameterValues("NCA_Kim2011")
model = pybamm.lithium_ion.DFN()

solver = pybamm.CasadiSolver(mode="safe")

current_input = np.array([0, 0.5, 0.45, 0.47])
time_input = np.array([0, 1, 2, 3])

current_interpolant = pybamm.Interpolant(time_input, current_input, pybamm.t)
parameter_values["Current function [A]"] = current_interpolant

sim = pybamm.Simulation(model, parameter_values=parameter_values, solver=solver)
sim.solve()
sol = sim.solution

```

The results are:  
`sol["Time [s]"].entries`  
array([0., 1., 2., 3.])

`sol["Current [A]"].entries`  
array([0. , 0.5 , 0.45, 0.47])

`sol["Terminal voltage [V]"].entries`  
array([4.07411821, 4.06341121, 4.06206838, 4.06012812])

I need to achieve the same results using `sim.step()`. Can anyone guide me on how to do that?

I followed the example in these discussions ([discussion-1](https://github.com/pybamm-team/PyBaMM/discussions/3126#discussion-5380026), [discussion-2](https://github.com/pybamm-team/PyBaMM/discussions/3416#discussion-5708287)). When I run each step, the current inputs get repeated and the results give me 7-8 entries instead of 4.

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<div class="post-metadata">

**Author:** ![appana.3](https://avatars.discourse-cdn.com/v4/letter/a/b782af/32.png) [@appana.3](https://pybamm.discourse.group/u/appana.3)\
**Post date:** [8 February 2025 21:36 UTC](https://pybamm.discourse.group/t/questions-about-simulation-step/146/2 "2025-02-08T21:36:10Z")

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Hi everyone,

Any input on this?

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<div class="post-metadata">

**Author:** ![appana.3](https://avatars.discourse-cdn.com/v4/letter/a/b782af/32.png) [@appana.3](https://pybamm.discourse.group/u/appana.3)\
**Post date:** [12 February 2025 05:50 UTC](https://pybamm.discourse.group/t/questions-about-simulation-step/146/3 "2025-02-12T05:50:31Z")

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I see that the newer PyBaMM version has the capability to resolve this issue!

Thank you