It returns a DataFrame with the data from the provided prices variable and column names names 'Jan', 'Feb and ,'Mar'. A god place to get information about Pandas DataFrame parameters is the documentation, for instance https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.DataFrame.html
What output? The empty line? That is expected? The line
header_dataframe=pd.DataFrame(prices,columns=['Jan','Feb','Mar'])
is a declaration.
Maybe you intended to execute more code? The page you linked to have more code and more outputs than you have provided. Tricky to know what you consider the issue to be here.
Anyway, next issue
Do you mean in the line: "11 77 68 70)" ? A bug in that version of Pandas? A mistake in the web page? I do not know but the page you link to says: Python version 3.6.5 (v3.6.5:f59c0932b4, Mar 28 2018, 16:07:46) [MSC v.1900 32 bit (Intel)] Pandas version 0.23.3 Matplotlib version 2.2.2
A test on: Python version 3.6.9 (default, Jul 17 2020, 12:50:27) [GCC 8.4.0] Pandas version 1.0.5 Matplotlib version 3.2.2 results in a last line:
11 77 68 70
So no parentheses at the end using newer versions.