Why is using a keyword like exec() or eval() in python not good coding?

Question

When I get a chance I enjoy using exec() for for to create dynamic namedtuples or maybe a widget in PyQt.
But why is this not good coding?

See an example below:
class App(QMainWidget):
def __init__(self):
super().__init__(self)
self.grid=QGridLayout()
txt = ('clear','next')
for n,t in enumerate(txt):
exec(f'b{n}=QPushButton(t)')
exec(f'self.grid.addWidget(b{n},2,{n+1})')
exec('b{n}.clicked.connect(self.{t})')
def clear(self):
pass
def next(self):
pass

obviously, above is incomplete code, but you get the picture

Answer 1

Your code should be PEP 8 complaint.

Also eval and exec are often marked as undesirable because of the complexity they induce. When you see a eval call you often don't know what's really going on behind it, because it acts on data that's usually in a variable. This makes code harder to read.

This seems to explain why better than I can.
http://stupidpythonideas.blogspot.com/2013/05/why-evalexec-is-bad.html