deref in a string into an operand

[John Doe]

I've got the action '+' stored as the variable 'plus',
that is plus='+'

Now I want to use the variable plus in an equation:
5 plus 7, just line 5 + 7

How do I do that?

Dan

 

[John Doe]

Foolish me; I examined the __builtin__ and found __getattribute__,
along with '__mul__' '__add__', '__sub__' and '__div__'.

So using a builtin object like 'x' ...

x = 5
attr = '__mul__'

print x.__getattribute__( attr )( 5 )
25

My program will store the operand as '__mul__' instead of '*', along with
a health bit of comment.

Dan. Closed.

 

[Peter Otten]

Foolish me; I examined the __builtin__ and found __getattribute__,
along with '__mul__' '__add__', '__sub__' and '__div__'.

So using a builtin object like 'x' ...

x = 5
attr = '__mul__'

print x.__getattribute__( attr )( 5 )
25

My program will store the operand as '__mul__' instead of '*', along with
a health bit of comment.

However, this may sometimes fail:
NotImplemented

Consider using the operator module instead:
2.0

Peter

 

[Steven Bethard]

So using a builtin object like 'x' ...

x = 5
attr = '__mul__'

print x.__getattribute__( attr )( 5 )
25

My program will store the operand as '__mul__' instead of '*', along with
a health bit of comment.

import operator
operator_map = {'+'perator.add, '-'perator.sub}
operator_map['+'](1, 2.0)

3.0

This allows you to call the add function whatever you want.

Steve

 

[Peter Abel]

I've got the action '+' stored as the variable 'plus',
that is plus='+'

Now I want to use the variable plus in an equation:
5 plus 7, just line 5 + 7

How do I do that?

Dan

If you want a string:
equation = '5 '+plus+' 7'

or

equation = '5 %s 7' % plus

Regards
Peter