Pandas DataFrames If else condition on multiple columns [duplicate]

I have a Data frame as shown below

import pandas as pd

df = pd.DataFrame({
    "name": ["john","peter","john","alex"],
    "height": [6,5,4,4],
    "shape": ["null","null","null","null"]
})

I want to apply this--- If name == john and height == 6 return shape = good else if height == 4 return shape = bad else change the shape to middle so the final Dataframe should look like this

  df = ({
        "name": ["john","peter","john","alex"],
        "height": [6,5,4,4],
        "shape": ["good","middle","bad","bad"]
    })

The only library I want to use is 'Pandas' and I do NOT want to use 'lambda' or 'NumPy'. Thanks in advance for your time. I will upvote your answers.