Python:检索表中每列索引后的值

Question

我想得到一个表格，其中每个单元格后面的值 = 100。有没有有效的方法来完成这个？

现在:

Col1 Col2 Col3 Col4
1    89   100  92
2    100  14   88
3    75   18   100
4    34   56   63

致:

Col1 Col2 Col3 Col4
1    nan  100  nan
2    100  14   nan
3    75   18   100
4    34   56   63

我已经尝试过:

for row in data:
    empty.append(str(np.where(element == 100 for element in row)));
for i in empty:
    #Not sure what to do next

Answer 1

解决您问题的矢量化方法:

>>> a = np.array([[89, 100, 92], [100, 14, 88],
...               [75, 18, 100], [34, 56, 63]])
>>> first100 = np.argmax(a == 100, axis=0)
>>> first100
array([1, 0, 2], dtype=int64)
>>> mask = rows[:, None] < first100
>>> mask
array([[ True, False,  True],
       [False, False,  True],
       [False, False, False],
       [False, False, False]], dtype=bool)
>>> out = a.astype(float)
>>> out[mask] = np.nan
>>> out
array([[  nan,  100.,   nan],
       [ 100.,   14.,   nan],
       [  75.,   18.,  100.],
       [  34.,   56.,   63.]])