# Python¶

## Import¶

The OSQP module can be imported with

import osqp


## Setup¶

The solver is initialized by creating an OSQP object

m = osqp.OSQP()


The problem is specified in the setup phase by running

m.setup(P=P, q=q, A=A, l=l, u=u, **settings)


The arguments q, l and u are numpy arrays. The elements of l and u can be $$\pm \infty$$ ( using numpy.inf).

The arguments P and A are scipy sparse matrices in CSC format. Matrix P can be either complete or just the upper triangular part. OSQP will make use of only the upper triangular part. If they are sparse matrices are in another format, the interface will attempt to convert them. There is no need to specify all the arguments.

The keyword arguments **settings specify the solver settings. The allowed parameters are defined in Solver settings.

## Solve¶

The problem can be solved by

results = m.solve()


The results object contains the primal solution x, the dual solution y, certificate of primal infeasibility prim_inf_cert, certificate of dual infeasibility dual_inf_cert and the info object containing the solver statistics defined in the following table

Member Description
iter Number of iterations
status Solver status
status_val Solver status value as in Status values
status_polish Polishing status
obj_val Objective value
pri_res Primal residual
dua_res Dual residual
setup_time Setup time
solve_time Solve time
update_time Update time
polish_time Polish time
run_time Total run time: setup/update + solve + polish
rho_estimate Optimal rho estimate
rho_updates Number of rho updates

Note that if multiple solves are executed from single setup, then after the first one run_time includes update_time + solve_time + polish_time.

## Update¶

Part of problem data and settings can be updated without requiring a new problem setup.

### Update problem vectors¶

Vectors q, l and u can be updated with new values q_new, l_new and u_new by just running

m.update(q=q_new, l=l_new, u=u_new)


The user does not have to specify all the keyword arguments.

### Update problem matrices¶

Matrices A and P can be updated by changing the value of their elements but not their sparsity pattern. The interface is designed to mimic the C/C++ counterpart. Note that the new values of P represent only the upper triangular part while A is always represented as a full matrix.

You can update the values of all the elements of P by executing

m.update(Px=Px_new)


If you want to update only some elements, you can pass

m.update(Px=Px_new, Px_idx=Px_new_idx)


where Px_new_idx is the vector of indices of mapping the elements of Px_new to the original vector Px representing the data of the sparse matrix P.

Matrix A can be changed in the same way. You can also change both matrices at the same time by running, for example

m.update(Px=Px_new, Px_idx=Px_new_idx, Ax=Ax_new, Ax=Ax_new_idx)


### Update settings¶

Settings can be updated by running

m.update_settings(**kwargs)


where kwargs are the settings that can be updated which are marked with an * in Solver settings.

## Warm start¶

OSQP automatically warm starts primal and dual variables from the previous QP solution. If you would like to warm start their values manually, you can use

m.warm_start(x=x0, y=y0)


where x0 and y0 are the new primal and dual variables.