【Python】iloc , iat の速度比較。DataFrameの選択に使うべきは？

df = pd.DataFrame([["a0","b0","c0"], ["a1","b1","c1"], ["a2","b2","c2"]],
                  columns=['A', 'B', 'C'])
display(df)

＃1行目を抜き出し
df.iloc[0]

#1行目の1列目を抜き出し
df.iloc[0,0]

#1,2行目の1,2列目を抜き出し
df.iloc[[0,1],[0,1]]

#1～2行目の1～3列目を抜き出し　※終了位置に指定した番号は含まれない
df.iloc[0:2,0:3]

#3行目より前の行の1列目より後の列を抜き出し
df.iloc[:2,1:]

#最終行から2行上～最終行の一列目より後～最終列
df.iloc[[0,1],[0,1]]

#全範囲選択　※df.iloc[,]とdf.iloc[ ,:]はエラー
df.iloc[:,:]
＃または
df.iloc[:,]

#1行目以後かつ2行目以前の行を抜き出し
df.iloc[lambda x: (x.index >= 0) & (x.index <= 1)]

#1行目の1列目を抜き出し
df.iat[0,0]

#ilocの所要時間
mea=[]
for s in range(1,50):
    df_iloc2=df
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        df_iloc2[i] = 0
        
    start = time.time()
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        for j in range(0,9999):
            df_iloc2[i][j] = df[i].iloc[j]
    calculation_time = time.time() - start
    print ("calculation_time:{0}".format(calculation_time) + "[s]")
    mea.append(calculation_time)

print("average")
print ("calculation_time:{0}".format(mean(mea)) + "[s]")

#iatの所要時間
mea=[]
for s in range(1,50):
    df_iat=df
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        df_iat[i] = 0
        
    start = time.time()
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        for j in range(0,9999):
            df_iat[i][j] = df[i].iat[j]
    calculation_time = time.time() - start
    print ("calculation_time:{0}".format(calculation_time) + "[s]")
    mea.append(calculation_time)

print("average")
print ("calculation_time:{0}".format(mean(mea)) + "[s]")

#iloc列ごと
mea=[]
for s in range(1,50):
    df_iloc=df
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        df_iloc[i] = 0
        
    start = time.time()
    for i in ["A","B","C","D","E","F","G","H","I","J"]:
        df_iloc[i] = df[i].iloc[:].values
    calculation_time = time.time() - start
    print ("calculation_time:{0}".format(calculation_time) + "[s]")

    mea.append(calculation_time)
print("average")
print ("calculation_time:{0}".format(mean(mea)) + "[s]")