pandas DataFrame, how to apply function to a specific column?

Question

I have read the docs of DataFrame.apply

DataFrame.apply(func, axis=0, broadcast=False, raw=False, reduce=None, args=(), **kwds)¶ Applies function along

Answer 1

The answer is,

df['A'] = df['A'].map(addOne)

and maybe you would be better to know about the difference of map, applymap, apply.

but if you insist to use apply, you could try like below.

def addOne(v):
    v['A'] += 1
    return v

df.apply(addOne, axis=1)

Answer 2

One simple way would be:

df['A'] = df['A'].apply(lambda x: x+1)

Answer 3

you can use .apply() with lambda function to solve this kind of problems.

Consider, your dataframe is something like this,

A | B | C
----------
1 | 4 | 7
2 | 5 | 8
3 | 6 | 9

The function which you want to apply:

def addOne(v):
v += 1
return v

So if you write your code like this,

df['A'] = df.apply(lambda x: addOne(x.A), axis=1)

You will get:

A | B | C
----------
2 | 4 | 7
3 | 5 | 8
4 | 6 | 9