If the relevant entries in Charge_Per_Line are empty (NaN) when you read into pandas, you can use df.dropna:
df = df.dropna(axis=0, subset=['Charge_Per_Line'])
If the values are genuinely -, then you can replace them with np.nan and then use df.dropna:
import numpy as np
df['Charge_Per_Line'] = df['Charge_Per_Line'].replace('-', np.nan)
df = df.dropna(axis=0, subset=['Charge_Per_Line'])