pandas: Bug on .to_string(index=False)

Code Sample, a copy-pastable example if possible

Related issue (very old though) #11833

import pandas

print("pandas.__version__ == {:s}".format(pandas.__version__))

columns = ['name', 'age']
values = [
    ['name_one', '31'],
    ['name_two', '32']]
data_frame = pandas.DataFrame(values, columns=columns)

# filter

filtered = data_frame[(data_frame['name'] == 'name_one') & (data_frame['age'] == '31')]
# single value comes with a blank at the beginning when running 0.24.0

print("==={:s}===".format(filtered.name.to_string(index=False)))

The output of this running on pandas 0.24.0 is: (I put this in a file called pandasbug.py)

(goodman_pipeline) [simon@ctioy9 sandbox]$ python3.7 pandasbug.py 
pandas.__version__ == 0.24.0
=== name_one===

Problem description

Exactly when 0.24.0 was released my automatic builds started to fail. The problem, a file not found. This was erroneously reported by me on astropy/ccdproc#658 I’m using a pandas data frame to filter a set of reference files and when extracting the file name and join it to a full path it turns out a non-existing path such as: /full/path/to/[unwanted-blank-here]file_name.fits (/full/path/to/ file_name.fits)

This travis build will show the real-world error caused, if you can access it.

Expected Output

In my system I have pandas 0.20.3 working with python 3.6 and the latests working build ran pandas 0.23.4

(goodman_pipeline) [simon@ctioy9 sandbox]$ python3.6 pandasbug.py 
pandas.__version__ == 0.20.3
===name_one===

Output of pd.show_versions()

>>> import pandas >>> pandas.show_versions()

INSTALLED VERSIONS

commit: None python: 3.7.2.final.0 python-bits: 64 OS: Linux OS-release: 4.9.0-1.el7.elrepo.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: en_US.UTF-8

pandas: 0.24.0 pytest: 4.1.1 pip: 18.1 setuptools: 40.6.3 Cython: 0.29.2 numpy: 1.15.2 scipy: 1.2.0 pyarrow: None xarray: None IPython: None sphinx: 1.8.3 patsy: None dateutil: 2.7.5 pytz: 2018.9 blosc: None bottleneck: None tables: None numexpr: None feather: None matplotlib: 3.0.1 openpyxl: None xlrd: None xlwt: None xlsxwriter: None lxml.etree: None bs4: None html5lib: None sqlalchemy: None pymysql: None psycopg2: None jinja2: 2.10 s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: None gcsfs: None