I studied this problem before writing the post, but I could not overcome it. Pycharm does a line break when displaying a dataframe if it has a large number of columns.
I've already added line
pd.set_option('display.max_columns', 3000)
Also I tried
df.to_string()
It really helps, but all my DataFrames have millions of rows, so it is not a very convenient way. My be there is a setting in PyCharm NOT to do the line wrap?