for if loop to categorize under condition

I am pretty new to python and used to use R. For this matter, I would use as.factor and categorize based on the number.

Earlier I was trying to use replace and .loc function in order to give a new category value in a new column according to the condition but it would run only to fail at what I wanted to do.

Eventually I created the following, very simple function:

g['Category'] = ""

for i in g['NumFloorsGroup']:
    if i == '0-9' or i == '10-19':
        g['Category'] = 'LowFl'
    elif i == '50~':
        g['Category'] = 'HighFl'
    else:
        g['Category'] = 'NormalFl'

When I run the function though, it only returns the 'LowFl' and doesn't correct the other parts. I feel like I am missing something.

the data info is as follows:

<class 'pandas.core.frame.DataFrame'>
Int64Index: 596 entries, 128 to 595
Data columns (total 4 columns):
YearBuilt         596 non-null int64
NumFloorsGroup    596 non-null category
Count             596 non-null int64
Category          596 non-null object
dtypes: category(1), int64(2), object(1)

Any comment will be helpful!