import pandas as pd

df = pd.DataFrame({'A': ["a", "b", "c"], 'B': [4, 5, 6]})

def modify_string(a):
    return a.upper() + "1"

def add_one(a):
    return a + 1

df['A'] = df['A'].apply(modify_string)
df['B'] = df['B'].apply(add_one)

df

import pandas as pd

df = pd.DataFrame({'A': ["a", "b", "c"], 'B': [4, 5, 6]})


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

df

import pandas as pd

df = pd.DataFrame({'A': ["a", "b", "c"], 'B': [4, 5, 6]})


df['A'] = df['A'].str.upper() + "1"
df['B'] += 1

df