Naming columns in pandas deletes data

Question

The code below gives me this table:

raw = pd.read_clipboard() raw.head() +---+---------------------+-------------+---------+----------+-------------+ | | Afghanistan | South Asia | 652225 | 26000000 | Unnamed: 4 | +---+---------------------+-------------+---------+----------+-------------+ | 0 | Albania | Europe | 28728 | 3200000 | 6656000000 | | 1 | Algeria | Middle East | 2400000 | 32900000 | 75012000000 | | 2 | Andorra | Europe | 468 | 64000 | NaN | | 3 | Angola | Africa | 1250000 | 14500000 | 14935000000 | | 4 | Antigua and Barbuda | Americas | 442 | 77000 | 770000000 | +---+---------------------+-------------+---------+----------+-------------+

But when I attempt to rename the columns and create a DataFrame, all of the data disappears:

df = pd.DataFrame(raw, columns = ['name', 'region', 'area', 'population', 'gdp']) df.head() +---+------+--------+------+------------+-----+ | | name | region | area | population | gdp | +---+------+--------+------+------------+-----+ | 0 | NaN | NaN | NaN | NaN | NaN | | 1 | NaN | NaN | NaN | NaN | NaN | | 2 | NaN | NaN | NaN | NaN | NaN | | 3 | NaN | NaN | NaN | NaN | NaN | | 4 | NaN | NaN | NaN | NaN | NaN | +---+------+--------+------+------------+-----+

Any idea why?

Why are you making a new DataFrame instead of just doing df.columns = ['name', 'region', ...]? Also, it looks like your data has no header, so the initial read is reading the first row as column names. Might want to fix that by passing header=None to read_clipboard. — BrenBarn
– BrenBarn, Commented Aug 14, 2014 at 1:44
This fixes my problems. If you post it as an answer I'll accept it. — metersk
– metersk, Commented Aug 14, 2014 at 1:52

DataSwede · Accepted Answer · 2014-08-14 15:53:14Z

You should just write:

df.columns = ['name', 'region', ...]

This is also much more efficient as you aren't trying to copy the entire DataFrame; as far as I know passing one DataFrame into the constructor for another will make a deep, not shallow copy.

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