Fixed parameter for Map() in python

Question

Is there anyway to user map on a list with one fixed parameter without a for loop? for example

def addx(x, y):
  return x + y

print map(addx, 10, [10,20])

output should be 20 and 30

Thanks

Answer 1

functools.partial() to the rescue:

from functools import partial

map(partial(addx, 10), [10, 20])

Demo:

>>> from functools import partial
>>>
>>> def addx(x, y):
...   return x + y
... 
>>> map(partial(addx, 10), [10, 20])
[20, 30]

Answer 2

You can also use list comprehensions:

def addx(x, y):
    return x + y

print [addx(10, i) for i in [10,20]]

Answer 3

You can also use repeat from itertools:

from itertools import repeat

def addx(x, y):
  return x + y

map(addx, repeat(10), [10,20])

---

Side note: if you are using Executor.map() from ProcessPoolExecutor, it's likely to get into trouble with a lambda method, as the passed function to map should be a top-level module function to be picklable:
https://stackoverflow.com/a/8805244/3366323