Python: When using a for loop to create list, if blank insert value?

I have the following code:

 for car in car_list:
        specs = car.find_elements(By.XPATH, ".//li[@class='sc-kcuKUB bMKvpn']")
        car_specs = []
        for spec in specs:
                entry = spec.get_attribute('innerHTML')
                entry = spec.text
                car_specs.append(entry)
        all_specs.append(car_specs)

Which correctly produces output such as the following:

print(all_specs):

> ['2021 (21 reg)', 'SUV', '35,008 miles', '395BHP', 'Automatic',
> 'Electric', '1 owner'] [['2021 (21 reg)', 'SUV', '35,008 miles',
> '395BHP', 'Automatic', 'Electric', '1 owner']]

However, sometimes the specs for a car are blank, resulting in the following:

> ['2021 (21 reg)', 'SUV', '35,008 miles', '395BHP', 'Automatic',
> 'Electric', '1 owner'] [['2021 (21 reg)', 'SUV', '35,008 miles',
> '395BHP', 'Automatic', 'Electric', '1 owner'] []]

(Note the empty list at the end)

When I come to concat this dataframe to another, there is a row transposition issue as there is a blank list in this dataframe, but not in the other.

How can I insert a text value to at least populate the list if spec or specs are blank?

I have tried the following:

for spec in specs:
            if spec is None:
                car_specs.append('texthere')
            else:
                entry = spec.get_attribute('innerHTML')
                entry = spec.text
                car_specs.append(entry)

If the car has no specs, then you can just bypass adding it or add a placeholder:

all_specs = []
for car in car_list:
    specs = car.find_elements(By.XPATH, ".//li[@class='sc-kcuKUB bMKvpn']")
    car_specs = [
        spec.text.strip()
        for spec in specs
        if spec.text.strip()
    ]
    all_specs.append(car_specs or ["no specs found"])

for car in car_list:
    specs = car.find_elements(By.XPATH, ".//li[@class='sc-kcuKUB bMKvpn']")
    car_specs = []
    if len(specs) == 0:
        car_specs.append('texthere')
    for spec in specs: 
            entry = spec.get_attribute('innerHTML')
            entry = spec.text
            car_specs.append(entry)
    all_specs.append(car_specs)

Edit: I edited my previous answer because I did read your problem wrong

Your problem is probably caused by the fact that if specs is empty ( 0 size list), you append an empty list ( car_specs = [] ) to your definitive list

To solve this problem, at each iteration check the size of specs, if it's 0 then you know it's empty