[英]Apply a function with arguments to each row using df.apply()
當所應用的函數非常瑣碎(例如.upper()或簡單乘法)時,我已經看到足夠多的關於使用df.apply()函數的問題。 但是,當我嘗試應用自定義函數時,會不斷出現各種錯誤。 我不知道從哪里開始這個錯誤:
這是我的簡化示例:
我的虛假數據:
inp = [{'c1':10, 'c2':1}, {'c1':11,'c2':110}, {'c1':12,'c2':0}]
df1 = pd.DataFrame(inp)
print(df1)
我的假功能
def fake_funk(row, upper, lower):
if lower < row['c1'] < upper:
return(1)
elif row['c2'] > upper:
return(2)
else:
return(0)
測試它確實有效:
for index, row in df1.iterrows():
print(fake_funk(row,11,1))
1
2
0
現在使用apply()
df1.apply(lambda row,: fake_funk(row,11,1))
我得到的錯誤很長:
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc (pandas/_libs/index.c:5126)()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.Int64HashTable.get_item (pandas/_libs/hashtable.c:14010)()
TypeError: an integer is required
During handling of the above exception, another exception occurred:
KeyError Traceback (most recent call last)
<ipython-input-116-a554e891e761> in <module>()
----> 1 df1.apply(lambda row,: fake_funk(row,11,1))
/usr/local/anaconda3/lib/python3.5/site-packages/pandas/core/frame.py in apply(self, func, axis, broadcast, raw, reduce, args, **kwds)
4260 f, axis,
4261 reduce=reduce,
-> 4262 ignore_failures=ignore_failures)
4263 else:
4264 return self._apply_broadcast(f, axis)
/usr/local/anaconda3/lib/python3.5/site-packages/pandas/core/frame.py in _apply_standard(self, func, axis, ignore_failures, reduce)
4356 try:
4357 for i, v in enumerate(series_gen):
-> 4358 results[i] = func(v)
4359 keys.append(v.name)
4360 except Exception as e:
<ipython-input-116-a554e891e761> in <lambda>(row)
----> 1 df1.apply(lambda row,: fake_funk(row,11,1))
<ipython-input-115-e95f3470fb25> in fake_funk(row, upper, lower)
1 def fake_funk(row, upper, lower):
----> 2 if lower < row['c1'] < upper:
3 return(1)
4 elif row['c2'] > upper:
5 return(2)
/usr/local/anaconda3/lib/python3.5/site-packages/pandas/core/series.py in __getitem__(self, key)
599 key = com._apply_if_callable(key, self)
600 try:
--> 601 result = self.index.get_value(self, key)
602
603 if not is_scalar(result):
/usr/local/anaconda3/lib/python3.5/site-packages/pandas/core/indexes/base.py in get_value(self, series, key)
2475 try:
2476 return self._engine.get_value(s, k,
-> 2477 tz=getattr(series.dtype, 'tz', None))
2478 except KeyError as e1:
2479 if len(self) > 0 and self.inferred_type in ['integer', 'boolean']:
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_value (pandas/_libs/index.c:4404)()
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_value (pandas/_libs/index.c:4087)()
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc (pandas/_libs/index.c:5210)()
KeyError: ('c1', 'occurred at index c1')
默認情況下, apply
沿第0軸進行操作。 似乎您需要沿第一軸進行操作。 順便說一句,您也不需要lambda
。 只需傳遞一個args
參數,就足夠了。
df1.apply(fake_funk, axis=1, args=(11, 1))
0 1
1 2
2 0
dtype: int64
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