You can do this by printing out help('modules')
:
Only showing a few lines of the output since it is big
>>> help('modules')
Please wait a moment while I gather a list of all available modules...
IN aifc hmac sf
__future__ another html shelve
_ast antigravity http shlex
_bisect argparse idlelib shutil
_bootlocale array imaplib signal
_bz2 ast imghdr site
_codecs asynchat imp smtpd
_codecs_cn asyncio importlib smtplib
_codecs_hk asyncore inspect sndhdr
_codecs_iso2022 atexit io socket
_codecs_jp audioop ipaddress socketserver
_codecs_kr base64 itertools something
_codecs_tw bdb json sqlite3
_collections binascii keyword sre_compile
_collections_abc binhex lib2to3 sre_constants
_compat_pickle bisect linecache sre_parse
_compression builtins locale ssl
_crypt bz2 logging stat
_csv cProfile lzma statistics
_ctypes calendar macpath string
You could also narrow down by searching for matching words. For example, you want to lookup something that might match "collections":
>>> help('modules collections')
Here is a list of modules whose name or summary contains 'collections'.
If there are any, enter a module name to get more help.
_collections - High performance data structures.
_collections_abc - Abstract Base Classes (ABCs) for collections, according to PEP 3119.
collections
collections.__main__
collections.abc
test.test_collections - Unit tests for collections.py.
test.test_defaultdict - Unit tests for collections.defaultdict.
pip._vendor.requests.packages.urllib3._collections
Then, if you want help on a particular module, to get more information on it, you just call the help on that particular one:
>>> help('collections')