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Editorial Team
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Asked: 2026-06-03T06:51:31+00:00

I’m currently doing some stuffs with Python and I get some strange behavior when

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I’m currently doing some stuffs with Python and I get some strange behavior when assigning variables. For example, I set “a” to 0.1 in the ipython console :

In [1]: a = 0.1

Then I print a :

In [2]: a
Out[2]: 0.10000000000000001

In [3]: a == 0.1
Out[3]: True

In [4]: a == 0.10000000000000001
Out[4]: True

Okay, maybe it’s because of the finite representation of numbers (the last 1 is at the 16th place). But then :

In [17]: 1 == 0.10000000000000001
Out[17]: False

Do I have to be scared by this ? Because I am ! 😉

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1 Answer

  1. Editorial Team

    Check the Floating Point Arithmetic: Issues and Limitations part of the Python tutorials – what you describe is inherent weirdness with the float data type (nothing Python specific)

    Also, be aware that repr() (string representation) shows the float with pretty-looking rounding – your first a example isn’t exactly 0.1, which can be seen if you print it with more precision:

    >>> a
0.1
>>> print "%.50f" % a
0.10000000000000000555111512312578270211815834045410
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