Whining about "struct"

Terry Reedy tjreedy at udel.edu
Thu Oct 14 06:49:13 CEST 2010

On 10/14/2010 12:30 AM, Tim Roberts wrote:
> I have a bad memory.  I admit it.  Because of that, the Python "help"
> system is invaluable to me.  Up through Python 2.5, I could get a quick
> reference to the format specifiers for the struct module via
>    import struct; help(struct)
> I used that a LOT.
> But in Python 2.6, the struct module moved from Python code to C code, and
> that helpful help string was removed.
> Is that still gone in Python 3.1?  What are the chances of reinstating that
> helpful chart?

With 3.1, help(struct) includes the following:

     The optional first format char indicates byte order, size and 
       @: native order, size & alignment (default)
       =: native order, std. size & alignment
       <: little-endian, std. size & alignment
       >: big-endian, std. size & alignment
       !: same as >

     The remaining chars indicate types of args and must match exactly;
     these can be preceded by a decimal repeat count:
       x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;
       ?: _Bool (requires C99; if not available, char is used instead)
       h:short; H:unsigned short; i:int; I:unsigned int;
       l:long; L:unsigned long; f:float; d:double.
     Special cases (preceding decimal count indicates length):
       s:string (array of char); p: pascal string (with count byte).
     Special case (only available in native format):
       P:an integer type that is wide enough to hold a pointer.
     Special case (not in native mode unless 'long long' in platform C):
       q:long long; Q:unsigned long long
     Whitespace between formats is ignored.

If this does not cover what you were referring to, open an issue with 
*specific* suggestion for addition.

Terry Jan Reedy

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