Pandas报IndexError: tuple index out of range的原因排查

问题场景 #

执行代码 #

print("cp_name={}, oe_name={}, category={}".format(cp_name, oe_name, category))
print("DF After: mtm={}, tenor={}, limit={}, utilization={}".format(*tuple(ac_df.loc[(ac_df['COUNTERPARTY ID'] == cp_name) & (ac_df['OWN ENTITY ID'] == oe_name) & (ac_df['MEASURE TYPE'] == category)  & (ac_df['TENOR'] == 'Remaining'),['MTM','TENOR', 'LIMIT', 'UTILIZATION']].astype(str).values.flatten())))

触发错误 #

运行时输出如下错误：

cp_name=FX_FTA050377_LE, oe_name=BNS, category=FX Notional
Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/opt/rh/rh-python36/root/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "/opt/rh/rh-python36/root/lib/python3.6/site-packages/django/core/management/__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/opt/rh/rh-python36/root/lib/python3.6/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/opt/rh/rh-python36/root/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "/opt/rh/rh-python36/root/lib64/python3.6/contextlib.py", line 52, in inner
    return func(*args, **kwds)
  File "/app/ccl/util/pfeweb_command.py", line 288, in handle
    bulk_list, updates = self.proc(file_map, **options)
  File "/app/ccl/counterparty/management/commands/actualexposure_8pm_rpt.py", line 149, in proc
    print("DF After: mtm={}, tenor={}, limit={}, utilization={}".format(*tuple(ac_df.loc[(ac_df['COUNTERPARTY ID'] == cp_name) & (ac_df['OWN ENTITY ID'] == oe_name) & (ac_df['MEASURE TYPE'] == category)  & (ac_df['TENOR'] == 'Remaining'),['MTM','TENOR', 'LIMIT', 'UTILIZATION']].astype(str).values.flatten())))
IndexError: tuple index out of range

交互式环境测试正常 #

将变量替换为打印出的具体值后，在交互式环境执行可正常输出：

>>> print("DF After: mtm={}, tenor={}, limit={}, utilization={}".format(*tuple(ac_df.loc[(ac_df['COUNTERPARTY ID'] == 'FX_FTA050377_LE') & (ac_df['OWN ENTITY ID'] == 'BNS') & (ac_df['MEASURE TYPE'] == 'FX Notional')  & (ac_df['TENOR'] == 'Remaining'),['MTM','TENOR', 'LIMIT', 'UTILIZATION']].astype(str).values.flatten())))
DF After: mtm=-13662.69, tenor=Remaining, limit=0.0, utilization=0.0

异常原因 #

核心问题是代码运行时的查询未返回任何数据，导致format()方法缺少所需参数，具体有两种常见可能性：

1. DataFrame状态不一致
   代码运行时的ac_df和交互式环境中使用的ac_df不是同一个版本：可能代码执行到报错语句前，ac_df已经被其他逻辑修改（比如过滤、删除行，或者重新加载了不同的数据），此时用变量查询无法匹配到任何行，values.flatten()得到空数组，解包后没有参数传递给format()，触发IndexError。而交互式环境中使用的是未被修改的原始ac_df，所以能查询到结果。

2. 变量存在隐形字符
   打印出来的cp_name、oe_name或category看起来和手动输入的字符串一致，但实际包含隐形字符（比如多余空格、换行符、控制字符）。这些字符在打印时无法被肉眼识别，但会导致和DataFrame中的值不匹配，查询无结果。而手动输入的字符串没有这些隐形字符，因此能正常匹配到行。

内容的提问来源于stack exchange，提问作者techie11