Fill after the column 72 by default, as per:

Each line must be limited to 72 characters followed by the character sequence that denotes an end-of-line (EOL). The EOL sequence used by the RFC Editor will be the two-character sequence CR LF (Carriage Return followed by Line Feed). This limit includes any left-side indentation.

— RFC 7994

For flowing long blocks of text with fewer structural restrictions (docstrings or comments), the line length should be limited to 72 characters.

— PEP 8: Style Guide for Python Code

(setopt fill-column 72)