title.
As seen below, I cannot see the very end of the line of code.
To change width of cells in current notebook just enter
from IPython.core.display import display, HTML
display(HTML("<style>.container { width:100% !important; }</style>"))
As suggested by jjinking
If this is still not sufficient you could decrease font size by going to
.jupyter\custom\custom.css
and changing font size as suggested by James Draper