# Truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all()

Having issue filtering my result dataframe with an `or`

condition. I want my result `df`

to extract all column `_var_`

values that are above 0.25 and below -0.25. This logic below gives me an ambiguous truth value however it work when I split this filtering in two separate operations. What is happening here? not sure where to use the suggested `a.empty(), a.bool(), a.item(),a.any() or a.all()`

.

```
result = result[(result['var']>0.25) or (result['var']<-0.25)]
```

The `or`

and `and`

python statements require `truth`

-values. For `pandas`

these are considered ambiguous so you should use "bitwise" `|`

(or) or `&`

(and) operations:

```
result = result[(result['var']>0.25) | (result['var']<-0.25)]
```

These are overloaded for these kind of datastructures to yield the element-wise `or`

(or `and`

).

Just to add some more explanation to this statement:

The exception is thrown when you want to get the `bool`

of a `pandas.Series`

:

```
>>> import pandas as pd
>>> x = pd.Series([1])
>>> bool(x)
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
```

What you hit was a place where the operator **implicitly** converted the operands to `bool`

(you used `or`

but it also happens for `and`

, `if`

and `while`

):

```
>>> x or x
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
>>> x and x
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
>>> if x:
... print('fun')
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
>>> while x:
... print('fun')
ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
```

Besides these 4 statements there are several python functions that hide some `bool`

calls (like `any`

, `all`

, `filter`

, ...) these are normally not problematic with `pandas.Series`

but for completeness I wanted to mention these.

In your case the exception isn't really helpful, because it doesn't mention the **right alternatives**. For `and`

and `or`

you can use (if you want element-wise comparisons):

```
>>> import numpy as np
>>> np.logical_or(x, y)
```

or simply the `|`

operator:

```
>>> x | y
```

```
>>> np.logical_and(x, y)
```

or simply the `&`

operator:

```
>>> x & y
```

If you're using the operators then make sure you set your parenthesis correctly because of the operator precedence.

There are several logical numpy functions which *should* work on `pandas.Series`

.

The alternatives mentioned in the Exception are more suited if you encountered it when doing `if`

or `while`

. I'll shortly explain each of these:

- If you want to check if your Series is
**empty**:

```
>>> x = pd.Series([])
>>> x.empty
True
>>> x = pd.Series([1])
>>> x.empty
False
```

Python normally interprets the `len`

gth of containers (like `list`

, `tuple`

, ...) as truth-value if it has no explicit boolean interpretation. So if you want the python-like check, you could do: `if x.size`

or `if not x.empty`

instead of `if x`

.

- If your
`Series`

contains**one and only one**boolean value:

```
>>> x = pd.Series([100])
>>> (x > 50).bool()
True
>>> (x < 50).bool()
False
```

- If you want to check the
**first and only item**of your Series (like`.bool()`

but works even for not boolean contents):

```
>>> x = pd.Series([100])
>>> x.item()
100
```

- If you want to check if
**all**or**any**item is not-zero, not-empty or not-False:

```
>>> x = pd.Series([0, 1, 2])
>>> x.all() # because one element is zero
False
>>> x.any() # because one (or more) elements are non-zero
True
```

From: stackoverflow.com/q/36921951

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