to_numeric crashes python on empty dataframe column

[linar-jether]

Crash sample

In[2]: df = pd.DataFrame(columns=['maybe_empty_column'])
  ...: pd.to_numeric(df['maybe_empty_column'], errors='ignore')

Process finished with exit code -1073741819 (0xC0000005)

Problem description

When calling to_numeric on an empty DataFrame column, python crashes with an access violation exit code (0xC0000005).

Expected Output

Should return an empty series with default dtype for empty series (int64)

for some reason, some empty Series objects work and some don't:

empty_that_works = pd.Series(['blabla',])[1:]
pd.to_numeric(empty_that_works)

empty_that_doesnt_work = pd.Series(dtype=object)
pd.to_numeric(empty_that_doesnt_work)

Output of pd.show_versions()

# Paste the output here pd.show_versions() here INSTALLED VERSIONS ------------------ commit: None python: 2.7.12.final.0 python-bits: 64 OS: Windows OS-release: 8.1 machine: AMD64 processor: Intel64 Family 6 Model 60 Stepping 3, GenuineIntel byteorder: little LC_ALL: None LANG: None LOCALE: None.None pandas: 0.20.1 pytest: 3.0.7 pip: 9.0.1 setuptools: 34.3.1 Cython: None numpy: 1.12.1 scipy: 0.18.1 xarray: None IPython: 5.3.0 sphinx: None patsy: 0.4.1 dateutil: 2.6.0 pytz: 2016.10 blosc: None bottleneck: None tables: None numexpr: 2.6.2 feather: None matplotlib: 1.5.3 openpyxl: None xlrd: 1.0.0 xlwt: None xlsxwriter: None lxml: None bs4: 4.5.1 html5lib: 0.9999999 sqlalchemy: None pymysql: None psycopg2: None jinja2: 2.9.6 s3fs: None pandas_gbq: None pandas_datareader: None

[TomAugspurger]

Fixed in #16305 I believe (0.20.2 was released today, so you can try upgrading). Let me know if that doesn't fix it for you.