adding row generated inside a loop to a new data frame

Question

I have a for loop to iterate through every row of a data frame. Now, when certain expressions match, I want to add the matching row to a new data frame.

This is what I have done:

dfWithSand3 = pd.DataFrame()
for index, row in df.iterrows():
    if row['embarked'] == 'S' and row['pclass'] == 3:
        dfWithSand3.append(row)
print(dfWithSand3)

Here, pd is pandas and df is the data frame.

Whenever the expression below is True I want to add the row to the data frame dfWithSand3.

if row['embarked'] == 'S' and row['pclass'] == 3:

Right now the value of the data frame dfWithSand3 is:

Empty DataFrame
Columns: []
Index: []

Below is what a possible row value could look like

Unnamed: 0     600
survived         0
pclass           3
sex           male
age             42
sibsp            0
parch            0
fare          7.55
embarked         S

I don't know if row represents a data frame or not.

Also, how would I add row to the new data frame I have created?

Answer 1

IIUC you can do it this way:

dfWithSand3  = df.loc[(df.embarked == 'S') & (df.pclass == 3)].copy()

or if you don't want to preserve original index values:

dfWithSand3  = df.loc[(df.embarked == 'S') & (df.pclass == 3)].reset_index().copy()