Я создал фрейм данных только для репликации данных, но попробуйте это
# Import libraries
import pandas as pd
import numpy as np
from datetime import datetime
# Create DataFrame
df = pd.DataFrame({'Date':['2020-06-29','2020-07-06','2020-07-13'],
'Value': [5.63, 6.01, 5.83]})
# Convert to datetime datatype
df['Date'] = pd.to_datetime(df['Date'])
# Store minimum date and max date in variables
s_range = df['Date'].min()
e_range = df['Date'].max()
# Generate date ranges between oldest and newest date
dates = pd.DataFrame(list(pd.date_range(s_range, e_range)),columns=['Date'])
# Merge dates DataFrame with original DataFrame
new_df = pd.merge(df,dates,on='Date',how='right').sort_values(['Date'])
# Reset index
new_df.reset_index(drop=True, inplace=True)
# Forward fill NaN with missing data
new_df.ffill(inplace=True)
Date Value
0 2020-06-29 5.63
1 2020-06-30 5.63
2 2020-07-01 5.63
3 2020-07-02 5.63
4 2020-07-03 5.63
5 2020-07-04 5.63
6 2020-07-05 5.63
7 2020-07-06 6.01
8 2020-07-07 6.01
9 2020-07-08 6.01
10 2020-07-09 6.01
11 2020-07-10 6.01
12 2020-07-11 6.01
13 2020-07-12 6.01
14 2020-07-13 5.83