import scanpy as sc
#compute pca
sc.tl.pca(adata, svd_solver='arpack')
#compute neighbours
sc.pp.neighbors(adata, n_neighbors=4, n_pcs=20)
sc.tl.draw_graph(adata)
#compute louvain clusters
sc.tl.louvain(adata, resolution=1.0)
sc.pl.draw_graph(adata, color='louvain', legend_loc='on data')