JIYIK CN >

This tutorial explains how to insert()insert a column in a Pandas DataFrame using the method.

import pandas as pd

countries_df = pd.DataFrame(
    {
        "Country": ["Nepal", "Switzerland", "Germany", "Canada"],
        "Continent": ["Asia", "Europe", "Europe", "North America"],
        "Primary Language": ["Nepali", "French", "German", "English"],
    }
)
print("Countries DataFrame:")
print(countries_df, "\n")

Output:

Countries DataFrame:
       Country      Continent Primary Language
0        Nepal           Asia           Nepali
1  Switzerland         Europe           French
2      Germany         Europe           German
3       Canada  North America          English

We will use the DataFrame shown in the above example countries_dfto explain how to insert()insert a column in a Pandas DataFrame using the method.

pandas.DataFrame.insert()method

grammar

DataFrame.insert(loc, column, value, allow_duplicates=False)

It columninserts a column named DataFrameinto , with the value valuespecified by , at locposition .

Use insert()the method to insert a column with the same value for all rows

import pandas as pd

countries_df = pd.DataFrame(
    {
        "Country": ["Nepal", "Switzerland", "Germany", "Canada"],
        "Continent": ["Asia", "Europe", "Europe", "North America"],
        "Primary Language": ["Nepali", "French", "German", "English"],
    }
)
print("Countries DataFrame:")
print(countries_df, "\n")

countries_df.insert(3, "Capital", "Unknown")

print("Countries DataFrame after inserting Capital column:")
print(countries_df)

Output:

Countries DataFrame:
       Country      Continent Primary Language
0        Nepal           Asia           Nepali
1  Switzerland         Europe           French
2      Germany         Europe           German
3       Canada  North America          English

Countries DataFrame after inserting Capital column:
       Country      Continent Primary Language  Capital
0        Nepal           Asia           Nepali  Unknown
1  Switzerland         Europe           French  Unknown
2      Germany         Europe           German  Unknown
3       Canada  North America          English  Unknown

It inserts the Capital column at index in countries_dfthe DataFrame 3, with the Capital column value set to for all rows Unknown.

The position 0starts at , so 3the position refers to the column in the DataFrame 4.

Insert a column into a DataFrame, specifying the value for each row

If we want insert()to specify the values ​​for the columns to be inserted into each row using the method, we can insert()pass a list of values ​​as valuethe parameter in the method.

import pandas as pd

countries_df = pd.DataFrame(
    {
        "Country": ["Nepal", "Switzerland", "Germany", "Canada"],
        "Continent": ["Asia", "Europe", "Europe", "North America"],
        "Primary Language": ["Nepali", "French", "German", "English"],
    }
)
print("Countries DataFrame:")
print(countries_df, "\n")

capitals = ["Kathmandu", "Zurich", "Berlin", "Ottawa"]

countries_df.insert(2, "Capital", capitals)

print("Countries DataFrame after inserting Capital column:")
print(countries_df)

Output:

Countries DataFrame:
       Country      Continent Primary Language
0        Nepal           Asia           Nepali
1  Switzerland         Europe           French
2      Germany         Europe           German
3       Canada  North America          English

Countries DataFrame after inserting Capital column:
       Country      Continent    Capital Primary Language
0        Nepal           Asia  Kathmandu           Nepali
1  Switzerland         Europe     Zurich           French
2      Germany         Europe     Berlin           German
3       Canada  North America     Ottawa          English

It inserts the column countries_dfat index in the DataFrame and assigns the value of each row to the column in the DataFrame .2CapitalCapital

Set in insert()the method allow_duplicates = Trueto add an existing column

import pandas as pd

countries_df = pd.DataFrame(
    {
        "Country": ["Nepal", "Switzerland", "Germany", "Canada"],
        "Continent": ["Asia", "Europe", "Europe", "North America"],
        "Primary Language": ["Nepali", "French", "German", "English"],
        "Capital": ["Kathmandu", "Zurich", "Berlin", "Ottawa"],
    }
)
print("Countries DataFrame:")
print(countries_df, "\n")

capitals = ["Kathmandu", "Zurich", "Berlin", "Ottawa"]

countries_df.insert(4, "Capital", capitals, allow_duplicates=True)

print("Countries DataFrame after inserting Capital column:")
print(countries_df)

Output:

Countries DataFrame:
       Country      Continent Primary Language    Capital
0        Nepal           Asia           Nepali  Kathmandu
1  Switzerland         Europe           French     Zurich
2      Germany         Europe           German     Berlin
3       Canada  North America          English     Ottawa

Countries DataFrame after inserting Capital column:
       Country      Continent Primary Language    Capital    Capital
0        Nepal           Asia           Nepali  Kathmandu  Kathmandu
1  Switzerland         Europe           French     Zurich     Zurich
2      Germany         Europe           German     Berlin     Berlin
3       Canada  North America          English     Ottawa     Ottawa

It Capitaladds the column to countries_dfthe DataFrame, even though the column countries_dfalready exists in the DataFrame Capital.

If we try to insert a column that already exists in the DataFrame without insert()setting it in the method allow_duplicates = True, it will throw us an error message: ValueError: cannot insert column, already exists..