Please explain.

```
import statistics
x = [0,1]
statistics.mean(x)
## 0.5
```

**But:**

```
import numpy
import statistics
x = numpy.array([0,1])
statistics.mean(x)
## 0
```

I'm pretty sure it's a basic, well-known, over-discussed issue: please link to a duplicate, as I couldn't find one.

pythonpython-3.xnumpystatisticspython-internals answered 5 days ago jpp #1

The reason is there is a conversion method in the `statistics`

module which checks if a data type is a subclass of `int`

. This works for `int`

, but not for `np.int32`

.

```
import statistics
from fractions import Fraction
a = statistics._convert(Fraction('1/2'), int) # 0.5
b = statistics._convert(Fraction('1/2'), np.int32) # 0
def _convert(value, T):
"""Convert value to given numeric type T."""
if type(value) is T:
return value
#### THIS BIT WORKS FOR int BUT not for np.int32 ###
if issubclass(T, int) and value.denominator != 1:
T = float
try:
return T(value)
except TypeError:
if issubclass(T, Decimal):
return T(value.numerator)/T(value.denominator)
else:
raise
```

Therefore, you can either use `statistics`

with a list, or `numpy`

with an array:

- Use
`statistics.mean([0, 1])`

; or - Use
`np.mean(np.array([0, 1]))`

, or`np.array([0, 1]).mean()`

.