IPython, "name 'plt' not defined"

Question

I recently installed Atom as an IDE on my laptop, for university. I installed Hydrogen as a convenient solution to show some plots on the go. But whenever I run Hydrogen, I get this error:

NameError                                 Traceback (most recent call last)
< ipython-input-1-1eb00ff78cf2>  in <module>

----> 1 plt.show()


NameError: name 'plt' is not defined

However Matplotlib is working properly when executed normally, and IPython seems to do as well. This is the code I'm trying to run test-wise:

%matplotlib ipympl

import matplotlib.pyplot as plt

a_x=[1,2,3,4,5,6]
a_y=[1,2,3,4,5,6]

plt.plot(a_x, a_y)
plt.show()

A video of the problem is available here.

• Selected Run

• Resulting error

Thaddeus

Answer 1

• As shown in the OP, import matplotlib.pyplot as plt is present, but it didn't get executed.
  • You only executed the selected line (9) with plt.show(), not the whole file.
• You can see the problem by carefully reading the traceback. Line 9 in the script is line 1 in the traceback: ----> 1 plt.show()
• The solution is to run the whole file, not one line. Click Run All not Run.

Mortify

Answer 2

You have to import the library first. Add this at start of the code.-

from matplotlib import pyplot as plt

Browder

You have to import the library first. is not correct, and the canonical way to import pyplot is import matplotlib.pyplot as plt, as shown in the matplotlib User Guide – Tauten