learnpython.org - an online interactive Python tutorial

harrismh777 harrismh777 at charter.net
Fri Apr 22 08:38:21 CEST 2011

Heiko Wundram wrote:
> The difference between strong typing and weak typing is best described by:
> Python 2.6.5 (r265:79063, Jun 12 2010, 17:07:01)
> [GCC 4.3.4 20090804 (release) 1] on cygwin
> Type "help", "copyright", "credits" or "license" for more information.
>>>> >>>  1+'2'
> Traceback (most recent call last):
>    File "<stdin>", line 1, in<module>
> TypeError: unsupported operand type(s) for +: 'int' and 'str'
>>>> >>>

Yes. And you have managed to point out a serious flaw in the overall 
logic and consistency of Python, IMHO.

Strings should auto-type-promote to numbers if appropriate.

This behavior should occur in input() as well. If a 'number' string is 
entered and can be converted to a Python number (whatever I mean by that 
at the moment) then the string should be converted to a number (int or 
float as appropriate) and the input() should return a reference to the 
number type  ( a value );  otherwise, input() should return the string 
entered, or throw a type error.

If an operation like (+) is used to add  1 + '1' then the string should 
be converted to int and the addition should take place, returning a 
reference to object int (2).

My feelings about this are strongly influenced by my experiences with 
the REXX language on IBM's SAA systems--- OS/2 and VM/CMS. In REXX 
everything is a string... everything. If a string just happens to be a 
REXX number, then it can be manipulated as you might expect for a 
number.  Neither here, nor there... just that I believe Python could 
take advantage of the "Python Number" concept and provide for auto-type 
casting of string to number (int or float) as appropriate if the string 
meets the Python Number requirements.

Just an idea... again, probably got beat up long before my time, I'm 

kind regards,
m harris

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