trackintel write csv function allows writing non-trackintel format csv files

[henrymartin1]

At the moment it is possible to write a .csv file that does not correspond to trackintel standards with the write_csv functions. I think this is a problem because then you can not open the file later using a read_csv function. Said differently, I think that every file that is written using a trackintel write_csv function should be readable using a trackintel read_csv function and this is not the case at the moment if the write_csv function is called without the accessor (e.g., ti.io.write_staypoints_csv).

I think the problem is that the dataframe is not checked before writing and an easy solution would be to include a call of the accessor before writing the dataframe in order to validate it.

Here is some sample code:

import trackintel as ti

from shapely.geometry import Point
import pandas as pd
import geopandas as gpd
import datetime
p1 = Point(8.5067847, 47.4)
p2 = Point(8.5067847, 47.5)
p3 = Point(8.5067847, 47.6)

t1 = pd.Timestamp("1971-01-01 00:00:00", tz="utc")
t2 = pd.Timestamp("1971-01-01 05:00:00", tz="utc")
t3 = pd.Timestamp("1971-01-02 07:00:00", tz="utc")
one_hour = datetime.timedelta(hours=1)

list_dict = [
    {"user_id": 0, "started_at": t1, "finished_at": t2, "geom": p1},
    {"user_id": 0, "started_at": t2, "finished_at": t3, "geom": p2},
    {"user_id": 1, "started_at": t3, "finished_at": t3 + one_hour, "geom": p3},
]
sp = gpd.GeoDataFrame(data=list_dict, geometry="geom", crs="EPSG:4326")
sp.index.name = "id"

sp.rename(inplace=True, columns={"geom":"geometry"})
sp.drop(columns=['finished_at'], inplace=True)


ti.io.write_staypoints_csv(sp, "test2.csv")
sp2 = ti.io.read_staypoints_csv("test2.csv", geom_col="geometry")

This produces the following error:

Traceback (most recent call last):
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\pandas\core\indexes\base.py", line 3621, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas\_libs\index.pyx", line 136, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 163, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 5198, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 5206, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: 'finished_at'
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\IPython\core\interactiveshell.py", line 3441, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-13-818f93779dfc>", line 1, in <module>
    sp2 = ti.io.read_staypoints_csv("test2.csv", geom_col="geometry")
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\trackintel\io\file.py", line 30, in wrapper
    return func(*args, **kwargs)
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\trackintel\io\file.py", line 293, in read_staypoints_csv
    df["finished_at"] = pd.to_datetime(df["finished_at"])
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\pandas\core\frame.py", line 3505, in __getitem__
    indexer = self.columns.get_loc(key)
  File "C:\ProgramData\Anaconda3\envs\graphentropy\lib\site-packages\pandas\core\indexes\base.py", line 3623, in get_loc
    raise KeyError(key) from err
KeyError: 'finished_at'

[bifbof]

I also think this is a problem, but more of a problem with the way the library is set up.
We have two ways to access this function

ti.io.write_positionfixes(sp, "test2.csv")
sp.as_positionfixes.to_csv("test2.csv")

and in the latter the attributes are checked, which is the preferred way to access this function.
Now if we were to add a check to write_positionfixes, we would have this overhead twice.
But maybe this is not a big problem and we should add it anyway? What do you think?

[henrymartin1]

Hm... its true that this is a problem in the architecture and I don't really see an easy way out. Maybe if there is an easy way to tell the write_positionfixes function where the user is coming from and whether or not we can skip the validation?
If you have no specific idea, I would just add it anyways.

[bifbof]

We could use inspect.currentframe().f_back (stackoverflow) to get the callers frame, but I have to say that is really hacky. :D
Has one of us ever tested how much work that check is? Else I'll check the difference and just add the extra check if it isn't too much.

[henrymartin1]

The check runs assert obj.geometry.is_valid.all() which isn't great in terms of performance but I think we should just add the check to the write_csv functions and optimize performance later if necessary.

[hongyeehh]

Is this solved with #490? @bifbof