CODEWITHSUNDEEP
pythonpandasdataframe
chippycentra
chippycentra

Reputation: 3432

Round in pandas column scientific numbers

Hello I have a df such as :

COL1        COL2
0.005554    0.35200000000000004
5.622e-11   0.267
0.006999999999999999    0.307
2.129e-14   0.469
2.604e-14   0.39
1.395e-60   0.27899999999999997
8.589999999999998e-74   0.29600000000000004
1.025e-42   0.4270000000000001

I knwo how to roun the digit in the COL2 by using

df['COL2'] = df['COL2'].round(3)

but if I do the same for COL1 it only displays 0

how can I get instead:

COL1        COL2
0.005   0.352
5.622e-11   0.267
0.007   0.307
2.129e-14   0.469
2.604e-14   0.39
1.395e-60   0.279
8.560e-74   0.296
1.025e-42   0.427

in fact the big issue is here:

it displays : 8.589999999999998e-74 and I would like to keep only 3 number after the coma

8.590e-74

Upvotes: 1

Views: 2125

Answers (3)

nachtgoblin24
nachtgoblin24

Reputation: 66

are lines 1 and 3 of the resulting dataframe also 0? because all other lines are 0 when rounded to the 3rd decimal because 5.622e-11 is 0.00000000005622 thus rounded to 3 decimals it is 0.

Upvotes: 0

Darina
Darina

Reputation: 1632

You don't want to round the values in the first column - rounding means that the lower digits are gone. I think what you actually want to do is to change how Pandas displays the data on screen and not the actual values in the dataframe. The default is already scientific notation.

You can specify the display format for all columns like so (this will be showing the first three digits after the dot):

pd.set_option('display.float_format', lambda x: '%.3f' % x)

Since you want to keep the format of the first one but not of the second you might need to set the format for each column individually. You can use styling for column 2:

df.style.format({'COL2': '{:.3f}')

Edit: Since your answer is for saving to CSV, you'll need to pass this as an argument to to_csv: float_format='{:.3E}'. This will save all columns in scientific notation. If you only want this for column 1, you could try the solutions to this question.

Upvotes: 4

Martin Valgur
Martin Valgur

Reputation: 6322

Assuming you only want to do this for display purposes, you can set

pd.options.display.precision = 3
print(df)

or to only do so in a temporary context:

with pd.option_context('display.precision', 3):
    print(df)

Upvotes: 1

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