Python函数读取长度无效

Question

我正在尝试开发一个函数来检查VIN的长度并返回一个输出

为了测试，如果长度=17，我让它打印出vin。但是，它清楚地打印出所有内容。不知道我做错了什么

下面的代码示例

import pandas as pd

#initialization
df = pd.DataFrame(columns = ["vin"], data = ['LHJLC79U58B001633','SZC84294845693987','LFGTCKPA665700387','L8YTCKPV49Y010001',
                                         'LJ4TCBPV27Y010217','LFGTCKPM481006270','LFGTCKPM581004253','LTBPN8J00DC003107',
                                         '1A9LPEER3FC596536','1A9LREAR5FC596814','1A9LKEER2GC596611','1A9L0EAH9C596099',
                                         '22A000018'])

df['manufacturer'] = ['A','A','A','A','B','B','B','B','B','C','C','D','D']

#develop function
def check_vin(df):
    if len(df['vin'][1]) == 17:
        print(df['vin'])
    else:
        print('nogo')


#test the function
for index, row in df.iterrows():
    check_vin(df)

Answer 1

您只需找到17长度的行，如下所示

condition = (df["vin"].str.len() == 17)
print(df[condition])

Answer 2

这是因为您在每次迭代中都要求相同事物的长度（df['vin'][1]）

更改为

for index, row in df.iterrows():
   check_vin(row)

以及

def check_vin(r):
    if len(r.vin) == 17:
        print(r)
    else:
        print('nogo')

输出

LHJLC79U58B001633
SZC84294845693987
LFGTCKPA665700387
L8YTCKPV49Y010001
LJ4TCBPV27Y010217
LFGTCKPM481006270
LFGTCKPM581004253
LTBPN8J00DC003107
1A9LPEER3FC596536
1A9LREAR5FC596814
1A9LKEER2GC596611
nogo
nogo

Answer 3

不要手动迭代行。可以使用“将新列指定给条件逻辑”：

df['check'] = np.where(df['vin'].str.len().eq(17), df['vin'], 'nogo')

print(df)

                  vin manufacturer              check
0   LHJLC79U58B001633            A  LHJLC79U58B001633
1   SZC84294845693987            A  SZC84294845693987
2   LFGTCKPA665700387            A  LFGTCKPA665700387
3   L8YTCKPV49Y010001            A  L8YTCKPV49Y010001
4   LJ4TCBPV27Y010217            B  LJ4TCBPV27Y010217
5   LFGTCKPM481006270            B  LFGTCKPM481006270
6   LFGTCKPM581004253            B  LFGTCKPM581004253
7   LTBPN8J00DC003107            B  LTBPN8J00DC003107
8   1A9LPEER3FC596536            B  1A9LPEER3FC596536
9   1A9LREAR5FC596814            C  1A9LREAR5FC596814
10  1A9LKEER2GC596611            C  1A9LKEER2GC596611
11   1A9L0EAH9C596099            D               nogo
12          22A000018            D               nogo