Question

What would be an elegant way to map a two parameter lambda function to a list of values where the first parameter is constant and the second is taken from a list?

Example:

lambda x,y: x+y
x='a'
y=['2','4','8','16']

expected result:

['a2','a4','a8','a16']

Notes:

• This is just an example, the actual lambda function is more complicated
• Assume I can’t use list comprehension

Answer 1

You can use itertools.starmap

a = itertools.starmap(lambda x,y: x+y, zip(itertools.repeat(x), y))
a = list(a)

and you get your desired output.

BTW, both itertools.imap and Python3’s map will accept the following:

itertools.imap(lambda x,y: x+y, itertools.repeat(x), y)

The default Python2’s map will not stop at the end of y and will insert Nones…

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But a comprehension is much better

[x + num for num in y]