Python Pandas: differences between two dates in weeks?

Question

When trying to find differences between two dates in weeks:

import pandas as pd

def diff(start, end):
    x = millis(end) - millis(start)
    return x / (1000 * 60 * 60 * 24 * 7 * 1000)

def millis(s):
    return pd.to_datetime(s).to_datetime64()

diff("2013-06-10","2013-06-16")

As a result I get:

Out[15]: numpy.timedelta64(857,'ns')

Which is obviously wrong. Questions:

1. How to get the difference in weeks, not nanoseconds, rounded up to a whole value?

2. How to get value out of 'numpy.timedelta64' object?

Answer 1

I think you can convert to int by dividing by numpy scalar:

def diff(start, end):
    x = pd.to_datetime(end) - pd.to_datetime(start)
    return int(x / np.timedelta64(1, 'W'))

print (diff("2013-06-10","2013-06-16"))
0
print (diff("2013-06-10","2013-06-26"))
2

See frequency conversion.