[Python] Python list joining — include separator at the start or at the end

The output for ', '.join(['a', 'b', 'c', 'd']) is:

a, b, c, d


Is there a standard way in Python to achieve the following outputs instead?

# option 1, separator is also at the start
, a, b, c, d

# option 2, separator is also at the end
a, b, c, d,

# option 3, separator is both at the start and the end
, a, b, c, d,

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