2.4.2 String literal concatenation
Multiple adjacent string literals (delimited by whitespace), possibly using different
quoting conventions, are allowed, and their meaning is the same as their concatenation.
"hello" 'world' is equivalent to
This feature can be used to reduce the number of backslashes needed, to split long strings
conveniently across long lines, or even to add comments to parts of strings, for example:
re.compile("[A-Za-z_]" # letter or underscore
"[A-Za-z0-9_]*" # letter, digit or underscore
Note that this feature is defined at the syntactical level, but implemented at compile
time. The `+' operator must be used to concatenate string expressions at run time. Also
note that literal concatenation can use different quoting styles for each component (even
mixing raw strings and triple quoted strings).