Python 3, using old Python 2 scripts

[Krion]

Hi,

I have just installed the Python 3 version of Houdini to test out if I can use old code with it. I had read something about an included convert-script.

My own shelf tool which references an old python script in an own PYTHONPATH of mine produces this error:

Do I need to rewrite all my old code?

Thanks,

[kiryha]

There is no such a big difference between Python2 and 3, so re-writing should not be hard. 

In Python 3 "print" is not a statement anymore, it is a function, which means you have to place everything in parentheses: print ('Hello, World!')

[Stalkerx777]

On 3/10/2021 at 7:41 AM, kiryha said:

There is no such a big difference between Python2 and 3, so re-writing should not be hard. 

In Python 3 "print" is not a statement anymore, it is a function, which means you have to place everything in parentheses: print ('Hello, World!')

This is simply not true. There's a huge difference between python 2 and 3. There's a reason why there's still massive amounts of Python 2 code around even after 12 years since Python 3 came out.

Changes to import mechanics, strings and unicode, iterators, metaclasses just to name a few. Switching to Python 3 is not trivial.

For simple scripts, converting manually is a reasonable option, for bigger projects I use this tool: futurize

Quote

Do I need to rewrite all my old code?

Check out this guide: https://docs.python.org/3/howto/pyporting.html

Edited March 16, 2021 by Stalkerx777
typo

[kiryha]

18 hours ago, Stalkerx777 said:

There's a huge difference between python 2 and 3.

My bad, you are right. But I was assuming the script is quite simple, and in that case, I guess it can be easy to update.

[warnerarc]

If you are a beginner then I would suggest you to just learn Python3 as Python3 will take over Python2 by 2020. But, if you are interested in just the differences than I can tell you a few common difference a beginner should know like - Python 2 vs Python 3 : 

• In Python2 print is like a command but in Python3 print() is a function
• In Python2 the integer divide works in C/C++ style but Python3 will return the expected result. For example, In Python2 7/2 will return 3 but in Python3 it will return 3.5
• In Python 2, a string is by default ASCII. But in Python3 string is by default Unicode

 

[GDonkey]

Hi there,

I'm very new to learning Python and am running the latest version of Houdini with python 3.

I was trying to run a simple command from a tutorial ( but it's py2 ) . I figured out that you have to now do print("stuff").
In the tutorial

When I run the code with what I thought would be the correct change to syntax:

import hou

my_obj_context = hou.node('/obj')

my_geo = hou.node('/obj/geo1')

print (my_geo.children)

I get the following result:

<bound method Node.children of <hou.ObjNode of type geo at /obj/geo1>>

When I try in an older version of Houdini with py2 I get the actual list of nodes ( but with print my_geo.children() ).

I can't seem to find any tutorials or guides that can help me get into using python in houdini with version 3 and above. Any advise is welcome.

 

Edited September 1, 2021 by GDonkey
I'm bad at links :P

[pezetko]

23 hours ago, GDonkey said:

print (my_geo.children)

I get the following result:

<bound method Node.children of <hou.ObjNode of type geo at /obj/geo1>>

When I try in an older version of Houdini with py2 I get the actual list of nodes ( but with print my_geo.children() ).

Hi, you forget to call the method.
print (my_geo.children) prints that method object. Not calling it.

You need:

print(my_geo.children())

 

[GDonkey]

Thank you so much !