Replacing the corresponding column values in Python Pandas dataframe

Question

I have a data frame, say:

 Name Visits 0 Z 0 1 A 0 2 B 1 3 C 1 4 D 0 5 E 0

Now, I made a list with those names whose visits are 0, so it has Z, A, D, and E. Now, I randomly choose 2 names from these 4. Then, I want to increase the visits of these 2 people by 1. How do I reference only these 2 names, access their corresponding visits and alter it? [In python, Pandas] Thank you!

Answer 1

Here is a posible solution:

df.visit[df.visit == 0] += 1

Answer 2

If you already have list of who visited 0 times you can use pd.Series.isin to create a boolean mask for boolean indexing then increase corresponding values by 1

vals = ['Z', 'A', 'D', 'E']
m = df['Name'].isin(vals)
df.loc[m, 'Visits']+=1
# This only increases Z, A, D, E visits by 1

Answer 3

Try random.choice from number then assign value by index

df.loc[np.random.choice(df.index[df.Visits==0],2),'Visits'] += 1
df
Out[95]: 
  Name  Visits
0    Z       1
1    A       0
2    B       1
3    C       1
4    D       0
5    E       0