Keyword Analysis & Research: what does double underscore mean in python

Keyword Analysis

Keyword	CPC	PCC	Volume	Score	Length of keyword
what does double underscore mean in python	1.93	0.9	7341	55	42
what	1.37	0.3	5369	82	4
does	1.17	0.3	4024	11	4
double	1.72	0.7	7361	49	6
underscore	1.29	0.9	888	71	10
mean	1.93	0.9	1296	16	4
in	0.49	0.8	5899	33	2
python	0.05	0.2	1988	51	6

Keyword	CPC	PCC	Volume	Score
what does double underscore mean in python	1.88	0.7	2549	8