input: Write a function to rewrite the given code using list comprehensions. If the input contains a for loop to append items to a list based on a condition, the function should return the input rewritten using a list comprehension. If the input is not a valid Python code or does not contain a for loop, the function should return False.
  assert rewrite_with_comprehension("even_numbers = []\nfor i in range(1,21):\n    if i % 2 == 0:\n        even_numbers.append(i)") == "even_numbers = [i for i in range(1, 21) if i % 2 == 0]"
  assert rewrite_with_comprehension("odd_numbers = [i for i in range(1,10) if i % 2 != 0]") == False
  assert rewrite_with_comprehension("sample_list = []") == False
  assert rewrite_with_comprehension("") == False
output: def rewrite_with_comprehension(code):
      import ast
      try:
          tree = ast.parse(code)
          for node in ast.walk(tree):
              if isinstance(node, ast.For):
                  if isinstance(node.body[0], ast.Expr) and isinstance(node.body[0].value, ast.Call) and isinstance(node.body[0].value.func, ast.Attribute) and node.body[0].value.func.attr == 'append':
                      target = node.target.id
                      iter_obj = node.iter.id if isinstance(node.iter, ast.Name) else ast.unparse(node.iter)
                      if_cond = ast.unparse(node.test) if hasattr(node, 'test') else None
                      list_name = node.body[0].value.func.value.id
                      if if_cond:
                          return f"{list_name} = [{target} for {target} in {iter_obj} if {if_cond}]"
                      else:
                          return f"{list_name} = [{target} for {target} in {iter_obj}]"
          return False
      except SyntaxError:
          return False