How to return value if a number is withing a specified range in pandas

user_14294794 0
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I want to return a value (1,2,3,4 or 5) based on the range a number falls in. I want to define a function and apply the function to a column in a DataFrame using .apply().

In the code below, amount is a hypothetical column in a DataFrame. However, I get the error SyntaxError: invalid syntax on line elif >= 40 amount < 60: (I believe it will raise the same error on all other lines).

amount = pd.Series([20, 25, 65, 80])

def miles(amount):
    if 20 >= amount < 40:
        return 1
    elif >= 40 amount < 60:
        return 2
    elif >= 60 amount < 80:
        return 3
    elif >= 80 amount < 100:
        return 4
    elif >= 100 amount < 120:
        return 5
    else:
        pass

Any help is appreciated. Thank you!

pandas python
3 Answers

For this particular case, you are mapping discrete fixed-width integer ranges to a number. This can be solved using a linear transform. The offset in this case is 0.

amount = pd.Series([20, 25, 65, 80])
out = amount.divide(20).astype(int)
out
# returns:
0   1
1   1
2   3
3   4
dtype: int32

For a more general case where the binning is not fixed-width, you can use pd.cut.

pd.cut(amount, [20, 40, 60, 80, 100, 120], right=False, labels=[1,2,3,4,5]).astype(int)
# returns:
0   1
1   1
2   3
3   4
dtype: int32
user_50037560

You can use:

pd.cut(amount, range(20,121,20), labels = range(1,6), right = False)
#Output:
#0    1
#1    1
#2    3
#3    4
#dtype: category
#Categories (5, int64): [1 < 2 < 3 < 4 < 5]

The first argument is the pandas.Series you want to cut, the next one are the bins, labels associates every bin with a label, and right includes the rightmost edge of the bin when it's True.

For more details check the documentation: pandas.cut.

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