从DataFrame中的特定列中选择非空行，并对其他列进行子选择

Question

我有一个dataFrame有几个coulmns，所以我选择了一些coulmns来创建一个像这样的变量xtrain = df[['Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ]]我想从这些coulmns中删除主数据框架中的Survive coulmn所有的原始数据。

Answer 1

You can pass a boolean mask to your df based on notnull() of 'Survive' column and select the cols of interest:

In [2]:
# make some data
df = pd.DataFrame(np.random.randn(5,7), columns= ['Survive', 'Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ])
df['Survive'].iloc[2] = np.NaN
df
Out[2]:
    Survive       Age      Fare  Group_Size      deck    Pclass     Title
0  1.174206 -0.056846  0.454437    0.496695  1.401509 -2.078731 -1.024832
1  0.036843  1.060134  0.770625   -0.114912  0.118991 -0.317909  0.061022
2       NaN -0.132394 -0.236904   -0.324087  0.570660  0.758084 -0.176421
3 -2.145934 -0.020003 -0.777785    0.835467  1.498284 -1.371325  0.661991
4 -0.197144 -0.089806 -0.706548    1.621260  1.754292  0.725897  0.860482

Now pass a mask to loc to take only non NaN rows:

In [3]:
xtrain = df.loc[df['Survive'].notnull(), ['Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ]]
xtrain

Out[3]:
        Age      Fare  Group_Size      deck    Pclass     Title
0 -0.056846  0.454437    0.496695  1.401509 -2.078731 -1.024832
1  1.060134  0.770625   -0.114912  0.118991 -0.317909  0.061022
3 -0.020003 -0.777785    0.835467  1.498284 -1.371325  0.661991
4 -0.089806 -0.706548    1.621260  1.754292  0.725897  0.860482

Answer 2

Two alternatives because... well why not?
Both drop nan prior to column slicing. That's two call rather than EdChum's one call.

one

df.dropna(subset=['Survive'])[
    ['Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ]]

two

df.query('Survive == Survive')[
    ['Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ]]

Answer 3

Of course already given answers are correct. Here is a simple one liner of code that works as well.

xtrain = df[df['survive'].notnull()][['Age','Fare', 'Group_Size','deck', 'Pclass', 'Title' ]]