You're right that both iterate through something but `for` loops and comprehensions aren't used as if they were interchangeable.

For example, you'll sometimes see people do bad stuff like this:

  >>> lst = []
  >>> 
  >>> [lst.append(i + i) for i in range(10)]
  [None, None, None, None, None, None, None, None, None, None]
  >>> 
  >>> lst
  [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
  >>> 

When they should be doing this:

  >>> lst = []
  >>> 
  >>> for i in range(10):
  ...     lst.append(i + i)
  ... 
  >>> lst
  [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
  >>> 

Or just this:

  >>> lst = [i + i for i in range(10)]
  >>> 
  >>> lst
  [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
  >>>

To generate a list/dictionary/geneator from an input iterable, you use a comprehension of the appropriate type.

To iterate through it without doing one of those things, you use a for loop.

In “one obvious way to do it”, “it” refers to a concrete task; the same is not necessarily intended to be true of arbitrarily broad generalizations of classes of tasks.