【Python】CSVファイルを行ごとに読み込み、列を追加する方法

import tkinter as tk
import tkinter.filedialog as fd
import pandas as pd

file2='sample3.csv'
df = pd.read_csv(file2, encoding = 'shift-jis',header=None, names=['怪人', '戦闘力'])
#見出しを用意
df['災害レベル']=""#事前に列を用意

for i, row in df.iterrows():
  if row[1]>=90:
    df['災害レベル'][i] = "神"#3列目に災害レベルを入れる
  elif row[1]>=80:
    df['災害レベル'][i] = "竜"
  elif row[1]>=70:
    df['災害レベル'][i] = "鬼"
  elif row[1]>=60:
    df['災害レベル'][i] = "虎"
  else:
    df['災害レベル'][i] = "狼"

root =tk.Tk()
root.withdraw()

file=fd.asksaveasfilename(
initialfile="disaster_level",
defaultextension=".csv",
title="保存場所を選んでね",
filetypes=[("TEXT",".csv")]
)
with open(file,"w",encoding = 'shift-jis') as f:
  df.to_csv(f, index=False)#書き出す
  print("保存完了です")

import tkinter as tk
import tkinter.filedialog as fd
import pandas as pd

$pip install pandas

CSVファイルを読み込んで見出しを用意

file_csv='sample3.csv'
df = pd.read_csv(file_csv, encoding = 'shift-jis',header=None, names=['怪人', '戦闘力'])
#見出しを用意
df['災害レベル']=""#事前に列を用意

for i, row in df.iterrows():
  if row[1]>=90:
    df['災害レベル'][i] ="神"#3列目に災害レベルを入れる
  elif row[1]>=80:
    df['災害レベル'][i] ="竜"
  elif row[1]>=70:
    df['災害レベル'][i] ="鬼"
  elif row[1]>=60:
    df['災害レベル'][i] ="虎"
  else:
    df['災害レベル'][i] ="狼"

root =tk.Tk()
root.withdraw()

file=fd.asksaveasfilename(
initialfile="disaster_level",
defaultextension=".csv",
title="保存場所を選んでね",
filetypes=[("TEXT",".csv")]
)
with open(file,"w",encoding = 'shift-jis') as f:
  df.to_csv(f, index=False)#書き出す
  print("保存完了です")