pandas.read_csv gives FileNotFound error inside a loop - pandas

Question

pandas.read_csv is working properly when used as a single statement. But it is giving FileNotFoundError when it is being used inside a loop even though the file exists.
for filename in os.listdir("./Datasets/pollution"):
print(filename) # To check which file is under processing
df = pd.read_csv(filename, sep=",").head(1)
These above lines are giving this following error.
pollutionData184866.csv <----- The name of the file is printed properly.
Traceback (most recent call last):
File "/home/parnab/PycharmProjects/FinalYearProject/locationExtractor.py", line 13, in <module>
df = pd.read_csv(i, sep=",").head(1)
File "/usr/lib/python3.6/site-packages/pandas/io/parsers.py", line 646, in parser_f
return _read(filepath_or_buffer, kwds)
File "/usr/lib/python3.6/site-packages/pandas/io/parsers.py", line 389, in _read
parser = TextFileReader(filepath_or_buffer, **kwds)
File "/usr/lib/python3.6/site-packages/pandas/io/parsers.py", line 730, in __init__
self._make_engine(self.engine)
File "/usr/lib/python3.6/site-packages/pandas/io/parsers.py", line 923, in _make_engine
self._engine = CParserWrapper(self.f, **self.options)
File "/usr/lib/python3.6/site-packages/pandas/io/parsers.py", line 1390, in __init__
self._reader = _parser.TextReader(src, **kwds)
File "pandas/parser.pyx", line 373, in pandas.parser.TextReader.__cinit__ (pandas/parser.c:4184)
File "pandas/parser.pyx", line 667, in pandas.parser.TextReader._setup_parser_source (pandas/parser.c:8449)
FileNotFoundError: File b'pollutionData184866.csv' does not exist
But when I am doing
filename = 'pollutionData184866.csv'
df = pd.read_csv(filename, sep=',')
It is working fine.
What am I doing wrong?

Answer 1

os.listdir("./Datasets/pollution") returns a list of files without a path and according to the path "./Datasets/pollution" you are parsing CSV files NOT from the current directory ".", so changing it to glob.glob('./Datasets/pollution/*.csv') should work, because glob.glob() returns a list of satisfying files/directories including given path
Demo:
In [19]: os.listdir('d:/temp/.data/629509')
Out[19]:
['AAON_data.csv',
'AAON_data.png',
'AAPL_data.csv',
'AAPL_data.png',
'AAP_data.csv',
'AAP_data.png']
In [20]: glob.glob('d:/temp/.data/629509/*.csv')
Out[20]:
['d:/temp/.data/629509\\AAON_data.csv',
'd:/temp/.data/629509\\AAPL_data.csv',
'd:/temp/.data/629509\\AAP_data.csv']