为什么我的 apply pandas 函数将每个值都转换为 None 值？

Question

I am trying to update the values in a dataframe column. There are three different values in this column, which I will call Alive :

Alive
-
And NaN values.

So I wrote a function to change the values:

def update_vals(x):
    if x == "-":
        x = False
    if x == "NaN":
        x = np.nan
    else:
        x = True

ppl_dataframe['Alive'].apply(update_vals)

However, when I go to apply this function, it simply results in None values being applied across the entire column.

What am I doing wrong here?

Answer 1

your function doesn't have a return statement so by default it returns None , you could use:

def update_vals(x):
    if x == "-":
        return False
    if x == "NaN":  # if you have np.nan values you have to change with np.isnan(x)
        return np.nan
    else:
        return True

Answer 2

Do not use apply , np.select

import numpy as np 


s1=ppl_dataframe['Alive']=='-'
s2=ppl_dataframe['Alive']=='NaN'

np.select([s1,s2],[False, np.nan],default=True)