How to fill step by step DataFrame according to the indeces?-CodePudding

I have the following code:

import pandas as pd

df = pd.DataFrame(columns = ['A', 'B', 'C', 'D'])
df = df.append({'A': ['AB', 'C', 'CD', 'DC']}, ignore_index = True)
df.to_csv('df.csv', index = False)


# Another place in the code
a = 5
df = pd.read_csv('df.csv')
df = df.append({'B': a}, ignore_index = True)
df.to_csv('df.csv', index = False)

The code gives:

Desired result:

How to correct the code, please? I would like to set indexes when ['AB', 'C', 'CD', 'DC'] list is loaded.

CodePudding user response：

IIUC use:

df = pd.concat([df, pd.DataFrame({'A': ['AB', 'C', 'CD', 'DC']})])

Your solution:

df = df.append(pd.DataFrame({'A': ['AB', 'C', 'CD', 'DC']}))

In another columns are created missing values, so is possible replace them by:

a = 5
df = df.fillna(pd.DataFrame({'B': a}, index=[0]))

Another idea:

df.loc[0, 'B'] = a