I don't understand why this is a "syntax error"?

I am trying to make a list of messages that will be randomly chosen from. I keep getting syntax error, I'm trying to figure out what I've missed?

I have looked over the code and can't see anything, but I feel like there's something I don't know about, I tried online checkers, but they just say errror and don't show me what the error is ...

messageRnd = ['Countdown time!'(days_left)'','OMG! '(dayt_left)'days to go!!', 'Just a reminder, there are'(days_left)' days to go!', ' '(days_left)'days left!', 'T-'(days_left)' to takeoff.', 'did you know there are '(days_left) 'days until we takeoff?']

from random import randint 
while True:
    days_left = str(randint(0,100))
    messageRnd = ['Countdown time! ' + (days_left),
              'OMG! ' + (days_left) + ' days to go!!',
              'Just a reminder, there are ' + (days_left) + ' days to go!',
              (days_left) + ' days left!',
              'T-' + (days_left) + ' to takeoff.',
              'Did you know there are ' + (days_left) + ' days until we takeoff?']
    print(messageRnd[randint(0,len(messageRnd) - 1)].replace("days_left", days_left))

You cannot just put the variable name in, you need a , or + to concatenate. Here you need to use + as the variable would be treated as a separate entry in the list instead.

You would be far better off using an f string if you want to include many variables in a string as it is easier to type and read.

This allows you to have a more readable list, at the cost of having to redefine it if days_left changes:

from random import randint    
while True:
        days_left = str(randint(0,100))
        messageRnd = [f'Countdown time! {days_left}',
                    f'OMG! {days_left} days to go!!',
                    f'Just a reminder, there are {days_left} days to go!',
                    f'{days_left} days left!',
                    f'T-{days_left} to takeoff.',
                    f'Did you know there are {days_left} days until we take off?']
        print(messageRnd[randint(0,len(messageRnd) - 1)])

As Cmd858 said in the comments, you could also do the following to avoid having to redefine the list while having the readability advantage:

from random import randint 
messageRnd = ['Countdown time! days_left',
            'OMG! days_left days to go!!',
            'Just a reminder, there are days_left days to go!',
            'days_left days left!',
            'T-days_left to takeoff.',
            'Did you know there are days_left days until we take off?']
while True:
    days_left = str(randint(0,100))
    print(messageRnd[randint(0,len(messageRnd) - 1)].replace("days_left", days_left))