I have a dynamic DataFrame which works fine, but when there are no data to be added into the DataFrame I get an error. And therefore I need a solution to create an empty DataFrame with only the column names.

For now I have something like this:

df = pd.DataFrame(columns=COLUMN_NAMES) # Note that there are now row data inserted.

PS: It is important that the column names would still appear in a DataFrame.

But when I use it like this I get something like that as a result:

Index([], dtype='object')
Empty DataFrame

The "Empty DataFrame" part is good! But instead of the Index thing I need to still display the columns.

Edit:

An important thing that I found out: I am converting this DataFrame to a PDF using Jinja2, so therefore I'm calling out a method to first output it to HTML like that:

df.to_html()

This is where the columns get lost I think.

Edit2: In general, I followed this example: . The css is also from the link. That's what I do to send the dataframe to the PDF:

env = Environment(loader=FileSystemLoader('.'))
template = env.get_template("pdf_report_template.html")
template_vars = {"my_dataframe": df.to_html()}
html_out = template.render(template_vars)
HTML(string=html_out).write_pdf("my_pdf.pdf", stylesheets=["pdf_report_style.css"])

Edit3:

If I print out the dataframe right after creation I get the followin:

[0 rows x 9 columns]
Empty DataFrame
Columns: [column_a, column_b, column_c, column_d,
column_e, column_f, column_g,
column_h, column_i]
Index: []

That seems reasonable, but if I print out the template_vars:

'my_dataframe': '<table border="1">\n <tbody>\n <tr>\n <td>Index([], dtype=\'object\')</td>\n <td>Empty DataFrame</td>\n </tr>\n </tbody>\n</table>'

And it seems that the columns are missing already.

E4: If I print out the following:

print(df.to_html())

I get the following result already:

<table border="1"> <tbody> <tr> <td>Index([], dtype='object')</td> <td>Empty DataFrame</td> </tr> </tbody>
</table>

4 Answers

You can create an empty DataFrame with either column names or an Index:

In [4]: import pandas as pd
In [5]: df = pd.DataFrame(columns=['A','B','C','D','E','F','G'])
In [6]: df
Out[6]:
Empty DataFrame
Columns: [A, B, C, D, E, F, G]
Index: []

Or

In [7]: df = pd.DataFrame(index=range(1,10))
In [8]: df
Out[8]:
Empty DataFrame
Columns: []
Index: [1, 2, 3, 4, 5, 6, 7, 8, 9]

Edit: Even after your amendment with the .to_html, I can't reproduce. This:

df = pd.DataFrame(columns=['A','B','C','D','E','F','G'])
df.to_html('test.html')

Produces:

<table border="1"> <thead> <tr> <th></th> <th>A</th> <th>B</th> <th>C</th> <th>D</th> <th>E</th> <th>F</th> <th>G</th> </tr> </thead> <tbody> </tbody>
</table>

0

Are you looking for something like this?

 COLUMN_NAMES=['A','B','C','D','E','F','G'] df = pd.DataFrame(columns=COLUMN_NAMES) df.columns Index(['A', 'B', 'C', 'D', 'E', 'F', 'G'], dtype='object')

2

Creating colnames with iterating

df = pd.DataFrame(columns=['colname_' + str(i) for i in range(5)])
print(df)
# Empty DataFrame
# Columns: [colname_0, colname_1, colname_2, colname_3, colname_4]
# Index: []

to_html() operations

print(df.to_html())
# <table border="1">
# <thead>
# <tr>
# <th></th>
# <th>colname_0</th>
# <th>colname_1</th>
# <th>colname_2</th>
# <th>colname_3</th>
# <th>colname_4</th>
# </tr>
# </thead>
# <tbody>
# </tbody>
# </table>

this seems working

print(type(df.to_html()))
# <class 'str'>

The problem is caused by

when you create df like this

df = pd.DataFrame(columns=COLUMN_NAMES)

it has 0 rows × n columns, you need to create at least one row index by

df = pd.DataFrame(columns=COLUMN_NAMES, index=[0])

now it has 1 rows × n columns. You are be able to add data. Otherwise its df that only consist colnames object(like a string list).

1

df.to_html() has a columns parameter.

Just pass the columns into the to_html() method.

df.to_html(columns=['A','B','C','D','E','F','G'])

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