I have this excel function where it says:
=IF(id ="pre_stage";"a";IF(id="static";"b";"c"))
I tried to implement this in my python script to create a new column.
df['type'] = df['id'].apply(lambda x: 'a' if x == 'pre_stage' else 'b')
I miss to put the second condition, where if the 'id' is 'static' then the type should be 'b', and other will be 'c'.
How is the script supposed to write?
Thank you
Instead of using a lambda, you can pass in a function to apply:
def f(x):
if x == 'pre_stage':
return 'a'
elif x == 'static':
return 'b'
return 'c'
df['type'] = df['id'].apply(f)
You can also use a dictionary:
d = {'pre_stage': 'a', 'static': 'b'}
df['type'] = df['id'].apply(lambda x: d.get(x, 'c'))
You can create a mapping and use pd.Series.map here.
mapping = {"pre_stage": "a", "static": "b"}
df["type"] = df["id"].map(mapping).fillna("c")
You can use np.select here.
condlist = [df["id"].eq("pre_stage"), df["id"].eq("static")]
choicelist = ["a", "b"]
df["type"] = np.select(condlist, choicelist, "c")
If your conditions are going to be nested, its better to define a function for it. It also helps to make your code clearer.
import pandas as pd
df = pd.DataFrame({'type':['pre-stage','static','not-related']})
def func(x):
if x == 'pre-stage':
return 'a'
elif x == 'static':
return 'b'
return 'c'
Result:
df['type'].apply(func) #as example, you can assign it to the frame as you did
>>
0 a
1 b
2 c
Name: type, dtype: object
