Rounding two similar numbers and getting different results Python

Question

I am trying to compare two different values in Python: 59.725 and 59.72497.

I am rounding them both using the Python round function as doing df.round(2) doesn't work how I need it to:

def round_df_columns(df, col_list):
        for col_name in col_list:
            for x in df[col_name]:
                rounded_x = round(x, 2)
                df[col_name] = df[col_name].replace(x, rounded_x)
        return df

However, when I do this I get 59.73 and 59.72. Is there a way of rounding these values so that they both round up to 59.73? I couldn't find a similar question, but sorry if this is a duplicate. Thanks!

That's...correct rounding by Python? Below 5 and round down, 5 and above round up. If you're desperate to round everything up, you could just round(x+0.005, 2). — Pam
– Pam, Commented Jun 29, 2022 at 13:27
You could multiply both numbers by 100, use the ceiling function (math.ceil), and then divide them by 100 again. But the behaviour you've seen from the rounding is mathematically correct - 59.72497 is less than 59.725 (i.e. less than halfway to 59.73) so should round to 59.72 — LowIntHighCha
– LowIntHighCha, Commented Jun 29, 2022 at 13:28

bekirbakar · Accepted Answer · 2022-06-29 13:38:45Z

2

Simple solution is using math.ceil.

Try

import math

x = math.ceil(100 * 59.72497) / 100
print(x)

y = math.ceil(100 * 59.725) / 100
print(y)

Ouput

59.73
59.73

edited Jun 29, 2022 at 13:38

answered Jun 29, 2022 at 13:33

bekirbakar

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Terminologist · Accepted Answer · 2022-06-29 13:29:53Z

1

If you want them to always round up, add 0.005 to the value before you round. E.g.

rounded_x = round(x + 0.005, 2)

answered Jun 29, 2022 at 13:29

Terminologist

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