python inline append to list and create a variable

I have syntax error in this line:

data = [{'name': project['name'], 'id': project['id']} for projects in api.all_projects() project = projects.to_dict() if project['name'].startswith('name')]

I’m not sure where’s the problem.

Error message when I run the python cli:

>>> data = [{'name': project['name'], 'id': project['id']} for projects in api.all_projects() project = projects.to_dict() if project['name'].startswith('name')]
  File "<stdin>", line 1
    data = [{'name': project['name'], 'id': project['id']} for projects in api.all_projects() project = projects.to_dict() if project['name'].startswith('name')]
                                                                                              ^^^^^^^
SyntaxError: invalid syntax

>Solution :

You can’t perform arbitrary assignment after the iteration statement; project = projects.to_dict() is not allowed where you put it.

You can use the walrus operator/assignment expression (:=) from 3.8+ as part of the if to achieve a similar effect though:

data = [{'name': project['name'], 'id': project['id']}
        for projects in api.all_projects()
        if (project := projects.to_dict())['name'].startswith('name')]

Other solutions, which avoid leaking the walrus-assigned variable, but are typically more verbose or ugly in one way or another, include:

1. Second loop over one-tuple or one-element list:

   data = [{'name': project['name'], 'id': project['id']}
           for projects in api.all_projects()
           for project in [projects.to_dict()]  # for project in (projects.to_dict(),) also works
           if (project['name'].startswith('name')]
   

2. map-ing with known class’s method (if you actually know the class), or operator.methodcaller:

   data = [{'name': project['name'], 'id': project['id']}
           for project in map(Project.to_dict, api.all_projects())
           if (project['name'].startswith('name')]
   
   # Without knowing class
   from operator import methodcaller  # At top of file
   
   data = [{'name': project['name'], 'id': project['id']}
           for project in map(methodcaller('to_dict'), api.all_projects())
           if (project['name'].startswith('name')]
   

3. chepner’s inner generator expression solution (a somewhat more verbose Python-level version of the map-based solutions)