I'm checking if a dataframe is empty and then assigning a value if it is. Dataframe has columns "NAME" and "ROLE"

df = pd.DataFrame(columns = ['NAME', 'ROLE'])

if df.empty:
    df["NAME"] = "Jake"

After assigning "Jake" to "NAME". The dataframe is still empty like so:

but I want the dataframe to look like this:

CodePudding user response：

Assigning a scalar to a pandas dataframe sets each value in that column to the scalar. Since you have zero rows, df["NAME"] = "Jake" doesn't assign anything. If you assign a list however, the dataframe is extended for that list. To get a single row in the dataframe

df["NAME"] = ["Jake"]

You could create more rows by adding additional values to the list being assigned.

CodePudding user response：

As people are saying in the comments, there are no rows in your empty dataframe to assign the value "Jake" to the "Name" column. Showing that in the first example:

df = pd.DataFrame(columns=['Name','Role'])
df['Name'] = 'Jake'
print(df)

I'm guessing instead you want to add a row:

df = pd.DataFrame(columns=['Name','Role'])
df = df.append({'Name':'Jake','Role':None},ignore_index=True)
print(df)