Saving a scipy.sparse matrix directly as a regular txt file

I have a scipy.sparse matrix (csr_matrix()). But I need to save it to a file not in the .npz format but as a regular .txt or .csv file. My problem is that I don't have enough memory to convert the sparse matrix into a regular np.array() and then save it to a file. Is there a way to have the data as a sparse matrix in memory but save it directly as a regular matrix to the disk? Or is there a way to "unzip" a .npz file without loading it into memory inside Python?