How to modify row values in iteration-CodePudding

The row values are not changed in the following iteration:

>>> df
         species  population
panda       bear        1864
polar       bear       22000
koala  marsupial       80000
>>> for i, r in df.iterrows():
...     r['population']=r['population']*2
...
>>> df
         species  population
panda       bear        1864
polar       bear       22000
koala  marsupial       80000

Can anyone please show me how can I persist the changed values in the above iteration?

CodePudding user response：

That's because iterrows returns copies that are disconnected from your original (df).

Jeff Reback: You should NEVER modify something you are iterating over.

Use pandas.Series.mul instead :

df["population"] = df["population"].mul(2)

Output :

print(df)

         species  population
panda       bear        3728
polar       bear       44000
koala  marsupial      160000