Applying geometric operation on multiple GeoDataFrames

Question

I have a collection of geodataframes in my Python environment. How can I apply for each GeoDataFrame the same spatial operation using following manner and create a new variable with the reference that it was manipulated by attaching "_dissolved"?

shp_1 = gpd.read_file('test1.shp')
shp_2 = gpd.read_file('test2.shp')
shp_3 = gpd.read_file('test3.shp')

lst = [shp_1,shp_2,shp_3]

for i in lst:
    
    i = i.dissolve(...)

Expected result would be the variables:

shp_1_dissolved
shp_2_dissolved
shp_3_dissolved

I tried something like:

i'_dissolved' = i.dissolve(...)

or

i + '_dissolved' = i.dissolve(...)

Answer 1

Use a dict

shps = ['test1.shp','test2.shp','test3.shp']

dfs = {}

for shp in shps:
    df = gpd.read_file(shp)
   
    dissolved_df = df.dissolve(...)

    dfs[shp] = df
    dfs[shp+'_dissolved'] = df_dissolved

Or

dfs = {}
dfs_dissolved = {}

for shp in shps:
    df = gpd.read_file(shp)
   
    dissolved_df = df.dissolve(...)

    dfs[shp] = df
    dfs_dissolved[shp] = df_dissolved

Answer 2

You need to get variable names. So you can use python exec method to create variable names using string. So that you can get variable names in a for loop.

I assume your file names are test1.shp, test2.shp, ..., test20.shp.

Try this script:

import geopandas as gpd

prefix = "shp_"
suffix = "_dissolved"
dissolve_by = "field_name" # CHANGE HERE
file_count = 20

# read shapefiles as GeoDataframes and assign it to shp_?
for i in range(1, file_count+1):
    # command is string here
    command = prefix + str(i) + ' = gpd.read_file("test' + str(i) + '.shp")'
    print ("Running: " + command)
    exec(command)

# Now, you can use shp_1 as variable
# print(shp_1)
    
# dissolve GeoDataFrames and assign it to shp_?_dissolved
for i in range(1, file_count+1):
    command=prefix + str(i) + suffix + ' = ' + prefix + str(i) + '.dissolve(by="' + dissolve_by + '")'
    print("Running: " + command)
    exec(command)

print("Done")

# Now, you can use shp_1_dissolved as variable
# print(shp_1_dissolved)

I must confess that this is not an appropriate way. But it'd be better use exec method to create a variable whose name depends on another variable name.