### 11. Data Persistence The modules described in this chapter support storing Python data in a persistent form on disk. The [pickle](# "pickle: Convert Python objects to streams of bytes and back.") and [marshal](# "marshal: Convert Python objects to streams of bytes and back (with different constraints).") modules can turn many Python data types into a stream of bytes and then recreate the objects from the bytes. The various DBM-related modules support a family of hash-based file formats that store a mapping of strings to other strings. The [bsddb](# "bsddb: Interface to Berkeley DB database library") module also provides such disk-based string-to-string mappings based on hashing, and also supports B-Tree and record-based formats.