How to check if float pandas column contains only integer numbers?

Question

I have a dataframe

df = pd.DataFrame(data=np.arange(10),columns=['v']).astype(float)

How to make sure that the numbers in v are whole numbers? I am very concerned about rounding/truncation/floating point representation errors

Answer 1

Here's a simpler, and probably faster, approach:

(df[col] % 1  == 0).all()

To ignore nulls:

(df[col].fillna(-9999) % 1  == 0).all()

Answer 2

If you want to check multiple float columns in your dataframe, you can do the following:

col_should_be_int = df.select_dtypes(include=['float']).applymap(float.is_integer).all()
float_to_int_cols = col_should_be_int[col_should_be_int].index
df.loc[:, float_to_int_cols] = df.loc[:, float_to_int_cols].astype(int)

Keep in mind that a float column, containing all integers will not get selected if it has np.NaN values. To cast float columns with missing values to integer, you need to fill/remove missing values, for example, with median imputation:

float_cols = df.select_dtypes(include=['float'])
float_cols = float_cols.fillna(float_cols.median().round()) # median imputation
col_should_be_int = float_cols.applymap(float.is_integer).all()
float_to_int_cols = col_should_be_int[col_should_be_int].index
df.loc[:, float_to_int_cols] = float_cols[float_to_int_cols].astype(int)

Answer 3

For completeness, Pandas v1.0+ offer the convert_dtypes() utility, that (among 3 other conversions) performs the requested operation for all dataframe-columns (or series) containing only integer numbers.

If you wanted to limit the conversion to a single column only, you could do the following:

>>> df.dtypes          # inspect previous dtypes
v                      float64

>>> df["v"] = df["v"].convert_dtype()
>>> df.dtypes          # inspect converted dtypes
v                      Int64

Answer 4

On 27 331 625 rows it works well. Time : 1.3sec

df['is_float'] = df[field_fact_qty]!=df[field_fact_qty].astype(int)

This way took Time : 4.9s

df[field_fact_qty].apply(lambda x : (x.is_integer()))