UltiSnips shows error with Python `If-Else`

Question

I am using UltiSnipswith vimtex as explained here and trying to use the snippet for Inline Math for LaTeX as shown in the link above. Everytime I try to execute the snippet it executes but immediately an error pops up in my vim.

Here is the snippet definition I am using :

snippet im "create an inline math environment" wAm
${$1}$`!p
if t[2] and t[2][0] not in [',', '.', '?', '-', ' ']:
    snip.rv = ' '
    else:
    snip.rv = ''
    `$2
endsnippet

And here is the error I am getting from vim :

An error occured. This is either a bug in UltiSnips or a bug in a
snippet definition. If you think this is a bug, please report it to
https://github.com/SirVer/ultisnips/issues/new
Please read and follow:
https://github.com/SirVer/ultisnips/blob/master/CONTRIBUTING.md#reproducing-bugs

Following is the full stack trace:
Traceback (most recent call last):
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/err_to_scratch_buffer.py", line 18, in wrapper
    return func(self, *args, **kwds)
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 896, in _track_change
    self._try_expand(autotrigger_only=True)
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 804, in _try_expand
    self._do_snippet(snippet, before)
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/snippet_manager.py", line 757, in _do_snippet
    text_before, self._visual_content, parent, start, end
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/snippet/definition/base.py", line 488, in launch
    snippet_instance.update_textobjects(vim_helper.buf)
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/text_objects/snippet_instance.py", line 93, in update_textobjects
    if obj._update(done, buf):
  File "/home/nitin/.vim/plugged/ultisnips/pythonx/UltiSnips/text_objects/python_code.py", line 268, in _update
    exec(code, self._locals)  # pylint:disable=exec-used
  File "<string>", line 4
    else:
       ^
SyntaxError: invalid syntax

Executed snippet code:
  1
  2   if t[2] and t[2][0] not in [',', '.', '?', '-', ' ']:
  3       snip.rv = ' '
  4       else:
  5       snip.rv = ''
  6 

Can anyone please help me figure out what is wrong and how to fix it?

Answer 1

It seems that when you copied the snippet you forgot to add the indentation spaces in the python snippet conditional code as shown in the error message:

Executed snippet code:
  1
  2   if t[2] and t[2][0] not in [',', '.', '?', '-', ' ']:
  3       snip.rv = ' '
  4       else:
  5       snip.rv = ''
  6 

Try to change it to:

snippet im "create an inline math environment" wAm
${$1}$`!p
if t[2] and t[2][0] not in [',', '.', '?', '-', ' ']:
    snip.rv = ' '
else:
    snip.rv = ''
    `$2
endsnippet