[FIXED] Complete list assigned to each row in python

Issue

I created a list as a mean of 2 other columns, the length of the list is same as the number of rows in the dataframe. But when I try to add that list as a column to the dataframe, the entire list gets assigned to each row instead of only corresponding values of the list.

glucose_mean = []
for i in range(len(df)):
    mean = (df['h1_glucose_max']+df['h1_glucose_min'])/2
    glucose_mean.append(mean)

df['glucose'] = glucose_mean

data after adding list

Solution

I think you overcomplicated it. You don't need for-loop but only one line

df['glucose'] = (df['h1_glucose_max'] + df['h1_glucose_min']) / 2

---

EDIT:

If you want to work with every row separatelly then you can use .apply()

def func(row):
   return (row['h1_glucose_max'] + row['h1_glucose_min']) / 2

df['glucose'] = df.apply(func, axis=1)

And if you really need to use for-loop then you can use .iterrows() (or similar functions)

glucose_mean = []

for index, row in df.iterrows():
    mean = (row['h1_glucose_max'] + row['h1_glucose_min']) / 2
    glucose_mean.append(mean)

df['glucose'] = glucose_mean

---

Minimal working example:

import pandas as pd

data = {
    'h1_glucose_min': [1,2,3], 
    'h1_glucose_max': [4,5,6], 
}

df = pd.DataFrame(data)

# - version 1 -

df['glucose_1'] = (df['h1_glucose_max'] + df['h1_glucose_min']) / 2

# - version 2 -

def func(row):
   return (row['h1_glucose_max'] + row['h1_glucose_min']) / 2

df['glucose_2'] = df.apply(func, axis=1)

# - version 3 -

glucose_mean = []

for index, row in df.iterrows():
    mean = (row['h1_glucose_max'] + row['h1_glucose_min']) / 2
    glucose_mean.append(mean)

df['glucose_3'] = glucose_mean

print(df)

Answered By - furas