Normal arguments vs keyword arguments

Question

How are  keyword arguments  different from regular arguments  Can t all arguments be passed as name value instead of using positional syntax

User · Answer

Just suplement add a way for defining the default value of arguments that is not assigned in key words when calling the function   def func   keywargs   if  my word  not in keywargs      word    default msg  else      word   keywargs  my word   return word   call this by   print func    print func my word  love      you ll get   default msg love   read more about  args and   kwargs in python  https   www digitalocean com community tutorials how-to-use-args-and-kwargs-in-python-3

User · Answer

There is one last language feature where the distinction is important  Consider the following function   def foo  positional    keywords       print  Positional    positional     print  Keywords    keywords   The  positional argument will store all of the positional arguments passed to foo    with no limit to how many you can provide    gt  gt  gt  foo  one    two    three   Positional    one    two    three   Keywords       The   keywords argument will store any keyword arguments    gt  gt  gt  foo a  one   b  two   c  three   Positional     Keywords    a    one    c    three    b    two     And of course  you can use both at the same time    gt  gt  gt  foo  one   two  c  three  d  four   Positional    one    two   Keywords    c    three    d    four     These features are rarely used  but occasionally they are very useful  and it s important to know which arguments are positional or keywords

User · Answer

Using Python 3 you can have both required and non-required keyword arguments     Optional   default value defined for param  b    def func1 a     b 42           func1 value for a    b is optional and will default to 42     Required  no default value defined for param  b     def func2 a     b            func2 value for a  b 21    b is set to 21 by the function call func2 value for a    ERROR  missing 1 required keyword-only argument   b     This can help in cases where you have many similar arguments next to each other especially if they are of the same type  in that case I prefer using named arguments or I create a custom class if arguments belong together

User · Answer

Using keyword arguments is the same thing as normal arguments except order doesn t matter  For example the two functions calls below are the same   def foo bar  baz       pass  foo 1  2  foo baz 2  bar 1

User · Answer

I m surprised that no one seems to have pointed out that one can pass a dictionary of keyed argument parameters  that satisfy the formal parameters  like so    gt  gt  gt  def func a  a   b  b   c  c     kwargs          print  a  s  b  s  c  s     a  b  c        gt  gt  gt  func   a a  b b  c c  gt  gt  gt  func     a     z    b   q    c   v    a z  b q  c v  gt  gt  gt

User · Answer

I m surprised no one has mentioned the fact that you can mix positional and keyword arguments to do sneaky things like this using  args and   kwargs  from this site    def test var kwargs farg    kwargs       print  formal arg    farg     for key in kwargs          print  another keyword arg   s   s     key  kwargs key     This allows you to use arbitrary keyword arguments that may have keys you don t want to define upfront

User · Answer

Positional Arguments  They have no keywords before them  The order is important   func 1 2 3   foo     Keyword Arguments  They have keywords in the front  They can be in any order   func foo  bar   baz 5  hello 123   func baz 5  foo  bar   hello 123    You should also know that if you use default arguments and neglect to insert the keywords  then the order will then matter   def func foo 1  baz 2  hello 3       func  bar   5  123

User · Answer

I was looking for an example that had default kwargs using type annotation   def test var kwarg a  str  b  str  B   c  str       kwargs  - gt  str       return     join  a  b  c  str kwargs      example    gt  gt  gt  print test var kwarg  A   c  okay    A B okay     gt  gt  gt  d     f    F    g    G    gt  gt  gt  print test var kwarg  a   c  c   b  b     d   a b c   f    F    g    G    gt  gt  gt  print test var kwarg  a    b    c    a b c

User · Answer

There are two related concepts  both called  keyword arguments    On the calling side  which is what other commenters have mentioned  you have the ability to specify some function arguments by name  You have to mention them after all of the arguments without names  positional arguments   and there must be default values for any parameters which were not mentioned at all   The other concept is on the function definition side  you can define a function that takes parameters by name -- and you don t even have to specify what those names are  These are pure keyword arguments  and can t be passed positionally  The syntax is  def my function arg1  arg2    kwargs    Any keyword arguments you pass into this function will be placed into a dictionary named kwargs  You can examine the keys of this dictionary at run-time  like this   def my function   kwargs       print str kwargs   my function a 12  b  abc      a   12   b    abc

User · Answer

There are two ways to assign argument values to function parameters  both are used    By Position   Positional arguments do not have keywords and are assigned first  By Keyword   Keyword arguments have keywords and are assigned second  after positional arguments    Note that you have the option to use positional arguments   If you don t use positional arguments  then -- yes -- everything you wrote turns out to be a keyword argument   When you call a function you make a decision to use position or keyword or a mixture   You can choose to do all keywords if you want   Some of us do not make this choice and use positional arguments

[python] Normal arguments vs. keyword arguments

Examples related to python

Examples related to arguments

Examples related to keyword

Examples related to optional-parameters

Examples related to named-parameters