CODEWITHSUNDEEP
pythonpandas
gogasca
gogasca

Reputation: 10058

Pandas add additional empty columns during DF creation

I'm getting:

AssertionError: 14 columns passed, passed data had 12 
columns.

Error is self-explanatory, I'm creating a DataFrame from a list of lists, each list in fact contains 12 fields. How can I force pandas.DataFrame to add extra columns with NaN in one operation. This is how Im creating the df.

pandas.DataFrame(results, columns=FIELDS)

Is there a way to simplify this in DataFrame creation, without having to do this:

pandas.DataFrame(results, columns=FIELDS_12)
df["ExtraField13"] = np.nan
df["ExtraField14"] = np.nan

Upvotes: 0

Views: 1923

Answers (1)

boot-scootin
boot-scootin

Reputation: 12515

Well, you don't really have to hard-code things like you have above with individual column assignments, line-by-line. This does a similar thing but uses a loop instead to pad columns:

>>> import pandas as pd
>>> df = pd.DataFrame({'A': [1,2,3], 'B': [4,5,6]})
>>> df
   A  B
0  1  4
1  2  5
2  3  6
>>> def pad_cols(df, n_cols):
...     while len(df.columns) < n_cols:
...         df['padded' + str(len(df.columns)+1)] = None
...     return df
... 
>>> pad_cols(df, 4)
   A  B padded3 padded4
0  1  4    None    None
1  2  5    None    None
2  3  6    None    None

Upvotes: 1

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