pass kwargs argument to another function with kwargs

Question

I do not understand the following example  lets say I have these functions     python likes def save filename  data    kwargs       fo   openX filename   w     kwargs     lt -  1     fo write data      fo close     python doesnt like def save2 filename  data    kwargs       fo   openX filename   w   kwargs     lt -  2     fo write data      fo close    def openX filename  mode    kwargs        doing something fancy and returning a file object   Why is  1 the right solution and  2 the wrong one    kwargs is basically a dict  so If I want to pass down the argument to openX I think the correct way would be without    and just giving the dict  But python obviously doesnt like the second one and tells me I gave 3 instead of 2 arguments  So whats the reason behind this

User · Answer

The    syntax tells Python to collect keyword arguments into a dictionary  The save2 is passing it down as a non-keyword argument  a dictionary object   The openX is not seeing any keyword arguments so the   args doesn t get used  It s instead getting a third non-keyword argument  the dictionary   To fix that change the definition of the openX function   def openX filename  mode  kwargs       pass

User · Answer

Expanding on  gecco  s answer  the following is an example that ll show you the difference   def foo   kwargs       for entry in kwargs items            print  Key      value      format entry 0   entry 1       call using normal keys  foo a 1  b 2  c 3    call using an unpacked dictionary  foo     a   1   b  2   c  3      call using a dictionary fails because the function will think you are   giving it a positional argument foo   a   1   b   2   c   3     this yields the same error as any other positional argument foo 3  foo  string      Here you can see how unpacking a dictionary works  and why sending an actual dictionary fails

User · Answer

For  2 args will be only a formal parameter with dict value  but not a keyword type parameter   If you want to pass a keyword type parameter into a keyword argument You need to specific    before your dictionary  which means    args  check this out for more detail on using   kw  http   www saltycrane com blog 2008 01 how-to-use-args-and-kwargs-in-python

User · Answer

Because a dictionary is a single value  You need to use keyword expansion if you want to pass it as a group of keyword arguments

User · Answer

In the second example you provide 3 arguments  filename  mode and a dictionary  kwargs   But Python expects  2 formal arguments plus keyword arguments   By prefixing the dictionary by      you unpack the dictionary kwargs to keywords arguments   A dictionary  type dict  is a single variable containing key-value pairs    Keyword arguments  are key-value method-parameters   Any dictionary can by unpacked to keyword arguments by prefixing it with    during function call

[python] pass kwargs argument to another function with kwargs

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[python] pass **kwargs argument to another function with **kwargs

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[python] pass kwargs argument to another function with kwargs