pandas dataframe drop problem, want to delete specific rows?

I have a problem to delete specific rows from my dataframe. I want to delete rows that are by matching account number. Here is code:

def main():
    # Collecting data from .csv
    df1 = pd.read_csv("./2018/Member last activited.csv", 
    sep=";", dtype={"Account Number": str}, encoding='ISO-8859-1', engine = 'python')

    accountnum = df1["Account Number"]

    # Collecting data from .csv
    df2 = pd.read_csv("./2019/Member last activited062019.csv", 
    sep=";", dtype={"Account Number": str, "Phone Number": str}, encoding='ISO-8859-1', engine = 'python')

    accountnum2 = df2["Account Number"]

    # comparing account numbers and removing them if matched
    tmp2 = {"ID": "0",
        "ACCOUNTNUM": "0"}
    tmplist = []
    for x, y in accountnum.items():
        for z, w in accountnum2.items():
            if y == w:
               tmp2 = {"ID": z, "ACCOUNTNUM": w }
    index = 0
    for x in df2["Account Number"]:
        if x == tmplist[index]["ACCOUNTNUM"]:
            df2.drop(index, inplace=True)
        index += 1 


You can use the .isin() method of pandas Series

df2["Account Number"].isin(df1["Account Number"])

This will give you Series of boolean values which will be true for all rows where Account Number in df2 is present in df1 as well. Since, you want to discard those rows, you can use series indexing along with ~ (negation operator) like this:

df3 = df2[~df2["Account Number"].isin(df1["Account Number"])]