Loop through geodataframe, append 0 values between 2001-2021

Question

I have produced a GeoPandas geodataframe (attached) with rows containing "loss_year" between 2001 and 2021, and some area values (pictured).

I wish to append the omitted years between 2001 - 2021 to the gdf, assigning 0 values to the geometry, area_ha and area_perc collumns. I will drop the geometry column before writing to a CSV.

Here is some pseudocode:

"""
for yr in 2000 - 2021:
    if yr not in gdf.loss_year:
          results.append({'loss_year'[yr], 'area_ha': 0.00, 'area_perc' : 0})
"""   

Answer 1

See: Missing data, insert rows in Pandas and fill with NAN

import geopandas as gpd
import pandas as pd
df = pd.DataFrame(gpd.read_file(r'C:\GIS\data\testdata\years.shp'))

#My dataframe have 3 rows/years: 2001, 2005, 2021:
#   loss_year   area  prc                                           geometry
#0       2001  42524    1  POLYGON ((14.71964 58.73581, 14.71703 59.05656...
#1       2005      1    1  POLYGON ((15.28429 58.93355, 15.28690 59.24807...
#2       2021    111    1  POLYGON ((14.62025 58.23570, 14.61672 58.56270...

df = df.set_index("loss_year").reindex(pd.Index(range(2001,2022,1), name="loss_year")).reset_index()
df = df[['loss_year','area','prc']].fillna(0)

#Now all the years from 2001-2021 are there:
# print(df.head(3))
#    loss_year     area  prc
# 0       2001  42524.0  1.0
# 1       2002      0.0  0.0
# 2       2003      0.0  0.0
# print(df.tail(3))
# 18       2019    0.0  0.0
# 19       2020    0.0  0.0
# 20       2021  111.0  1.0