Hand preprocessing data
If you have a really small dataset like a few 100 samples it's okay to do preporcessing via hand. But since you have a thousand samples it's better to automate the process. You can use the na_values attribute in pandas to fill in the &quot;???&quot; or &quot;??&quot; value with nan. Then for each column replace the Nan values using some statistical measure (in your case the most occuring word..etc). But if youre data-wrangling is unworkable via an automation process or takes too much time, then you should proceed manually. If it's about meeting a deadline a deadline the manual way works best for really messy data.