Update Pandas DF during while loop (Python3, Pandas) - python-3.x

Question

Some background: My code takes user input and applies it to my DF to remove certain rows. This process repeats as many times as the user would like. Unfortunately, I am not sure how to update my DF within the while loop I have created so that it keeps the changes being made:
data = ({'hello':['the man','is a','good guy']})
df = pd.DataFrame(data)
def func():
while True:
n = input('Words: ')
if n == "Done":
break
elif n != "Done":
pattern = '^'+''.join('(?=.*{})'.format(word) for word in n.split())
df[df['hello'].str.contains(pattern)==False]
How do I update the DF at the end of each loop so the changes being made stay put?

Answer 1

Ok, I reevaluated your problem and my old answer was totally wrong of course.
What you want is the DataFrame.drop method. This can be done inplace.
mask = df['hello'].str.contains(pattern)
df.drop(mask, inplace=True)
This will update your DataFrame.

Answer 2

Looks to me like you've already done all the hard work, but there are two problems.
Your last line doesn't store the result anywhere. Most Pandas operations are not "in-place", which means you have to store the result somewhere to be able to use it later.
df is a global variable, and setting its value inside a function doesn't work, unless you explicitly have a line stating global df. See the good answers to this question for more detail.
So I think you just need to do:
df = df[df['hello'].str.contains(pattern)==False]
to fix problem one.
For problem two, at the end of func, do return df then when you call func call it like:
df = func(df)
OR, start func with the line
global df