pandas - change df.index from float64 to unicode or string
Solution 1
You can do it that way:
# for Python 2
df.index = df.index.map(unicode)
# for Python 3 (the unicode type does not exist and is replaced by str)
df.index = df.index.map(str)
As for why you would proceed differently from when you'd convert from int to float, that's a peculiarity of numpy (the library on which pandas is based).
Every numpy array has a dtype, which is basically the machine type of its elements : in that manner, numpy deals directly with native types, not with Python objects, which explains how it is so fast. So when you are changing the dtype from int64 to float64, numpy will cast each element in the C code.
There's also a special dtype : object, that will basically provide a pointer toward a Python object.
If you want strings, you thus have to use the object dtype. But using .astype(object)
would not give you the answer you were looking for : it would instead create an index with object dtype, but put Python float objects inside.
Here, by using map, we convert the index to strings with the appropriate function: numpy gets the string objects and understand that the index has to have an object dtype, because that's the only dtype that can accomodate strings.
Solution 2
For python 3 and pandas 0.19 or latter versions, I found the following works fine for me
# Python 3 (pandas 0.19 or latter versions)
df.index.astype(str, copy = False)
Boosted_d16
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Updated on July 05, 2022Comments
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Boosted_d16 almost 2 years
I want to change a dataframes' index (rows) from float64 to string or unicode.
I thought this would work but apparently not:
#check type type(df.index) 'pandas.core.index.Float64Index' #change type to unicode if not isinstance(df.index, unicode): df.index = df.index.astype(unicode)
error message:
TypeError: Setting <class 'pandas.core.index.Float64Index'> dtype to anything other than float64 or object is not supported
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Shivam Gaur over 7 yearsThis doesn't work on Python 3.5. Do you have any idea why?
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Arthur over 7 yearsThe original poster was using Python 2. the
unicode
type does not exist anymore in Python 3, and thestr
type must be used instead (basically, what was calledstr
in Python 2 is calledbytes
in Python 3, andunicode
likewise becamestr
). See this question for more information. -
PMcK over 5 yearsI tried this in Python 3 and it did not change anything. I am trying to go change an index from Object to a String.
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AndreaCassioli over 5 years@PMcK I got the same issue. Any success?
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Michel de Ruiter over 4 yearsSometimes
df.index = df.index.astype(int)
is needed instead ofcopy=False
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VaM999 almost 4 years@MicheldeRuiter Could you tell me when assignment is needed instead of copy=False?
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Michel de Ruiter almost 4 years@VaM999 I don't remember... :-(
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Olivierwa about 3 yearsI had an issue when using copy=False and the type was np.uint64, The output would not be unsigned anymore
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smci about 2 yearsThis doesn't work for Python 3.8/pandas 1.3.4. Both with copy=True and False. Can you recheck and confirm which versions this works in?
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Admin about 2 yearsYour answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.