Hello,
I have tried the example to get data from alpha vantage (https://pandas-datareader.readthedocs.io/en/latest/remote_data.html#historical-time-series-data) and I got a ValueError:

Traceback (most recent call last):
File "adllib.py", line 40, in
api_key=os.getenv('ALPHAVANTAGE_API_KEY'))
File "/home/arne/dev/python/stock/venv/lib/python3.5/site-packages/pandas/util/_decorators.py", line 188, in wrapper
return func(*args, **kwargs)
File "/home/arne/dev/python/stock/venv/lib/python3.5/site-packages/pandas_datareader/data.py", line 579, in DataReader
api_key=api_key,
File "/home/arne/dev/python/stock/venv/lib/python3.5/site-packages/pandas_datareader/base.py", line 100, in read
return self._read_one_data(self.url, self.params)
File "/home/arne/dev/python/stock/venv/lib/python3.5/site-packages/pandas_datareader/base.py", line 112, in _read_one_data
return self._read_lines(out)
File "/home/arne/dev/python/stock/venv/lib/python3.5/site-packages/pandas_datareader/av/time_series.py", line 112, in _read_lines
raise ValueError("Please input a valid date range")
ValueError: Please input a valid date range

I have also tried the test procedure with pytest:

pytest -v test_av_time_series.py::TestAVTimeSeries::test_av_daily
============================================================================================================ test session starts ============================================================================================================
platform linux -- Python 3.5.2, pytest-5.3.2, py-1.8.1, pluggy-0.13.1 -- /home/arne/dev/python/stock/venv/bin/python
cachedir: .pytest_cache
rootdir: /home/arne/dev/python/stock
collected 1 item

test_av_time_series.py::TestAVTimeSeries::test_av_daily FAILED [100%]

================================================================================================================= FAILURES ==================================================================================================================
______________________________________________________________________________________________________ TestAVTimeSeries.test_av_daily _______________________________________________________________________________________________________

self = <pandas_datareader.tests.av.test_av_time_series.TestAVTimeSeries object at 0x7f85079867f0>

def test_av_daily(self):
    df = web.DataReader(
        "AAPL",
        "av-daily",
        start=self.start,
        end=self.end,
        retry_count=6,

      pause=20.5,

    )

test_av_time_series.py:63:

../../../pandas/util/_decorators.py:188: in wrapper
return func(*args, **kwargs)
../../data.py:579: in DataReader
api_key=api_key,
../../base.py:100: in read
return self._read_one_data(self.url, self.params)
../../base.py:112: in _read_one_data
return self._read_lines(out)

self = <pandas_datareader.av.time_series.AVTimeSeriesReader object at 0x7f8507984eb8>
out = {'Meta Data': {'1. Information': 'Daily Prices (open, high, low, close) and Volumes', '2. Symbol': 'AAPL', '3. Last Re..., '1999-12-30': {'1. open': '102.1900', '2. high': '104.1200', '3. low': '99.6200', '4. close': '100.3100', ...}, ...}}

def _read_lines(self, out):
    data = super(AVTimeSeriesReader, self)._read_lines(out)
    # reverse since alphavantage returns descending by date
    data = data[::-1]
    start_str = self.start.strftime("%Y-%m-%d")
    end_str = self.end.strftime("%Y-%m-%d")
    data = data.loc[start_str:end_str]
    if data.empty:

      raise ValueError("Please input a valid date range")

E ValueError: Please input a valid date range

../../av/time_series.py:112: ValueError

Best regards

arne