Can I set the default value when unpacking?

Question

I have the following:

>>> myString = "has spaces"
>>> first, second = myString.split()
>>> myString = "doesNotHaveSpaces"
>>> first, second = myString.split()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 1 value to unpack

I would like to have seconda default Noneif the string has no space. I currently have the following, but I am wondering if this can be done on one line:

splitted = myString.split(maxsplit=1)
first = splitted[0]
second = splitted[1:] or None

Answer 1

May I suggest you use a different method, i.e. partitioninstead of split:

>>> myString = "has spaces"
>>> left, separator, right = myString.partition(' ')
>>> left
'has'
>>> myString = "doesNotHaveSpaces"
>>> left, separator, right = myString.partition(' ')
>>> left
'doesNotHaveSpaces'

If you are on python3, you have this option:

>>> myString = "doesNotHaveSpaces"
>>> first, *rest = myString.split()
>>> first
'doesNotHaveSpaces'
>>> rest
[]

Answer 2

A general solution would be chainyour iterable using repeatvalues None, and then use the isliceresult:

from itertools import chain, islice, repeat

none_repat = repeat(None)
example_iter = iter(range(1)) #or range(2) or range(0)

first, second = islice(chain(example_iter, none_repeat), 2)

None, , ​​:

def fill_iter(it, size, fill_value=None):
    return islice(chain(it, repeat(fill_value)), size)

, , str.partition.

Answer 3

Here is one solution:

unpacker = lambda x,y=1,z=2:(x,y,z)

packed = (8,5)
a,b,c = unpacker(*packed)
print(a,b,c) # 8 5 2

packed = (8,)
a,b,c = unpacker(*packed)
print(a,b,c) # 8 1 2

Play with this code

Answer 4

You can try the following:

NUM2UNPACK=2   
parts = myString.split()    
first, second = parts+[None]*(NUM2UNPACK-(len(parts)))