# The truth value of a series is ambiguous. use a.empty, a.bool(), a.item(), a.any() or a.all()

## The truth value of a series is ambiguous. use a.empty, a.bool(), a.item(), a.any() or a.all()

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()
>>> 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)

>>> 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()
>>> 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()
>>> (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()
>>> 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 nonzero
True