[issue25193] itertools.accumlate should have an optional initializer argument

[Alun Champion]

New submission from Alun Champion:

itertools.accumulate should have an initializer with the same semantics as functools.reduce.
These two functions are closely related, reduce only providing you the end result accumulate providing an iterator over all the intermediate results.
However, if you want all the intermediate results to this reduce:

    functools.reduce(operator.mul, range(1, 4), 10)

You currently need to do:

    itertools.accumulate(itertools.chain([10], range(1,4), operator.mul)

Adding an optional initialiser argument would avoid this.

----------
components: Library (Lib)
messages: 251155
nosy: Alun Champion
priority: normal
severity: normal
status: open
title: itertools.accumlate should have an optional initializer argument
versions: Python 3.3, Python 3.4, Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue25193>
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