To change the level of a column from 0 to 1 in a data frame, you can use the replace() function. Here's an example code:

```{python} import pandas as pd

create a dataframe

df = pd.DataFrame({'col1': [0, 1, 0, 1], 'col2': ['A', 'B', 'C', 'D']}) print(df)

replace 0 with 1 in col1

df['col1'] = df['col1'].replace(0, 1) print(df)

Output:

col1 col2 0 0 A 1 1 B 2 0 C 3 1 D

col1 col2 0 1 A 1 1 B 2 1 C 3 1 D ```

In this example, we create a data frame with two columns (col1 and col2) and four rows. The col1 column contains 0s and 1s. To change all 0s to 1s, we use the replace() function with the parameters 0 and 1. The resulting data frame has all 0s replaced with 1s in the col1 column.