The right and elegant way to split a join a string in Python

Question

I have the following list:

>>> poly
'C:\\04-las_clip_inside_area\\16x16grids_1pp_fsa.shp'
>>> record
1373155

and I wish to create:

'C:\\04-las_clip_inside_area\\16x16grids_1pp_fsa_1373155.txt'

I wish to split in order to get the part "C:\04-las_clip_inside_area\16x16grids_1pp_fsa16x16grids_1pp_fsa".

I have tried this two-code-lines solution:

mylist = [poly.split(".")[0], "_", record, ".txt"]
>>> mylist
['C:\\04-las_clip_inside_area\\16x16grids_1pp_fsa', '_', 1373155, '.txt']

from here, reading the example in Python join, why is it string.join(list) instead of list.join(string)?.

I find this solution to joint, but I get this error message:

>>> mylist.join("")
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
AttributeError: 'list' object has no attribute 'join'

Also if I use:

>>> "".join(mylist)
Traceback (most recent call last):
  File "<interactive input>", line 1, in <module>
TypeError: sequence item 2: expected string, int found

Answer 1

Python join: why is it string.join(list) instead of list.join(string)?

So there is

"".join(mylist)

instead of

mylist.join("")

There's your error.

To solve your int/string problem, convert the int to string:

mylist= [poly.split(".")[0],"_",str(record),".txt"]

or write directly:

"{}_{}.txt".format(poly.split(".")[0], record)