The *args and **kwargs is a common idiom to allow arbitrary number of arguments to functions as described in the section more on defining functions in the Python documentation.
The *args will give you all function parameters as a tuple:
def foo(*args):
for a in args:
print(a)
foo(1)
# 1
foo(1,2,3)
# 1
# 2
# 3
The **kwargs will give you all
keyword arguments except for those corresponding to a formal parameter as a dictionary.
def bar(**kwargs):
for a in kwargs:
print(a, kwargs[a])
bar(name='one', age=27)
# name one
# age 27
Both idioms can be mixed with normal arguments to allow a set of fixed and some variable arguments:
def foo(kind, *args, **kwargs):
pass
It is also possible to use this the other way around:
def foo(a, b, c):
print(a, b, c)
obj = {'b':10, 'c':'lee'}
foo(100,**obj)
# 100 10 lee
Another usage of the *l idiom is to unpack argument lists when calling a function.
def foo(bar, lee):
print(bar, lee)
l = [1,2]
foo(*l)
# 1 2
In Python 3 it is possible to use *l on the left side of an assignment (Extended Iterable Unpacking), though it gives a list instead of a tuple in this context:
first, *rest = [1,2,3,4]
first, *l, last = [1,2,3,4]
Also Python 3 adds new semantic (refer PEP 3102):
def func(arg1, arg2, arg3, *, kwarg1, kwarg2):
pass
Such function accepts only 3 positional arguments, and everything after * can only be passed as keyword arguments.
Note:
- A Python
dict, semantically used for keyword argument passing, are arbitrarily ordered. However, in Python 3.6, keyword arguments are guaranteed to remember insertion order.
- "The order of elements in
**kwargs now corresponds to the order in which keyword arguments were passed to the function." - What’s New In Python 3.6
- In fact, all dicts in CPython 3.6 will remember insertion order as an implementation detail, this becomes standard in Python 3.7.
What is the line? You can just have arguments on the next line without any problems:
a = dostuff(blahblah1, blahblah2, blahblah3, blahblah4, blahblah5,
blahblah6, blahblah7)
Otherwise you can do something like this:
if (a == True and
b == False):
or with explicit line break:
if a == True and \
b == False:
Check the style guide for more information.
Using parentheses, your example can be written over multiple lines:
a = ('1' + '2' + '3' +
'4' + '5')
The same effect can be obtained using explicit line break:
a = '1' + '2' + '3' + \
'4' + '5'
Note that the style guide says that using the implicit continuation with parentheses is preferred, but in this particular case just adding parentheses around your expression is probably the wrong way to go.
Best Solution
You need to parenthesize your argument:
That should work.