You have a '\n'
at one of the list cells.
So when the iteration is trying to convert '\n'
to float it raise an ValueError
Try this code:
avg_energySTR = "5.50000e+000 5.50000e+001 5.50000e+002 5.50000e+003"
avg_energySTR = [str(i) for i in avg_energySTR.split()]
avg_energy = []
for stri in avg_energySTR:
tra = float(stri)
avg_energy.append(tra)
print (avg_energy)
You can also just split at the for itself:
avg_energySTR = "5.50000e+000 5.50000e+001 5.50000e+002 5.50000e+003 \n"
avg_energy = []
for stri in avg_energySTR.split():
.......