numpy.ndarray.tolist will do it:
a.tolist()
If your data is a pandas series you can call their tolist wrapper with the same result.
Answer from bigonazzi on Stack OverflowConvert numpy.int64 to python int in pandas - Stack Overflow
python - Convert float64 column to int64 in Pandas - Stack Overflow
Converting numpy dtypes to native python types - Stack Overflow
Trying to convert an Int64Index to an Int
Solution for pandas 0.24+ for converting numeric with missing values:
df = pd.DataFrame({'column name':[7500000.0,7500000.0, np.nan]})
print (df['column name'])
0 7500000.0
1 7500000.0
2 NaN
Name: column name, dtype: float64
df['column name'] = df['column name'].astype(np.int64)
ValueError: Cannot convert non-finite values (NA or inf) to integer
#http://pandas.pydata.org/pandas-docs/stable/user_guide/integer_na.html
df['column name'] = df['column name'].astype('Int64')
print (df['column name'])
0 7500000
1 7500000
2 NaN
Name: column name, dtype: Int64
I think you need cast to numpy.int64:
df['column name'].astype(np.int64)
Sample:
df = pd.DataFrame({'column name':[7500000.0,7500000.0]})
print (df['column name'])
0 7500000.0
1 7500000.0
Name: column name, dtype: float64
df['column name'] = df['column name'].astype(np.int64)
#same as
#df['column name'] = df['column name'].astype(pd.np.int64)
print (df['column name'])
0 7500000
1 7500000
Name: column name, dtype: int64
If some NaNs in columns need replace them to some int (e.g. 0) by fillna, because type of NaN is float:
df = pd.DataFrame({'column name':[7500000.0,np.nan]})
df['column name'] = df['column name'].fillna(0).astype(np.int64)
print (df['column name'])
0 7500000
1 0
Name: column name, dtype: int64
Also check documentation - missing data casting rules
EDIT:
Convert values with NaNs is buggy:
df = pd.DataFrame({'column name':[7500000.0,np.nan]})
df['column name'] = df['column name'].values.astype(np.int64)
print (df['column name'])
0 7500000
1 -9223372036854775808
Name: column name, dtype: int64
You can need to pass in the string 'int64':
>>> import pandas as pd
>>> df = pd.DataFrame({'a': [1.0, 2.0]}) # some test dataframe
>>> df['a'].astype('int64')
0 1
1 2
Name: a, dtype: int64
There are some alternative ways to specify 64-bit integers:
>>> df['a'].astype('i8') # integer with 8 bytes (64 bit)
0 1
1 2
Name: a, dtype: int64
>>> import numpy as np
>>> df['a'].astype(np.int64) # native numpy 64 bit integer
0 1
1 2
Name: a, dtype: int64
Or use np.int64 directly on your column (but it returns a numpy.array):
>>> np.int64(df['a'])
array([1, 2], dtype=int64)
Use val.item() to convert most NumPy values to a native Python type:
import numpy as np
# for example, numpy.float32 -> python float
val = np.float32(0)
pyval = val.item()
print(type(pyval)) # <class 'float'>
# and similar...
type(np.float64(0).item()) # <class 'float'>
type(np.uint32(0).item()) # <class 'int'>
type(np.int16(0).item()) # <class 'int'>
type(np.cfloat(0).item()) # <class 'complex'>
type(np.datetime64(0, 'D').item()) # <class 'datetime.date'>
type(np.datetime64('2001-01-01 00:00:00').item()) # <class 'datetime.datetime'>
type(np.timedelta64(0, 'D').item()) # <class 'datetime.timedelta'>
...
(A related method np.asscalar(val) was deprecated with 1.16, and removed with 1.23).
For the curious, to build a table of conversions of NumPy array scalars for your system:
for name in dir(np):
obj = getattr(np, name)
if hasattr(obj, 'dtype'):
try:
if 'time' in name:
npn = obj(0, 'D')
else:
npn = obj(0)
nat = npn.item()
print('{0} ({1!r}) -> {2}'.format(name, npn.dtype.char, type(nat)))
except:
pass
There are a few NumPy types that have no native Python equivalent on some systems, including: clongdouble, clongfloat, complex192, complex256, float128, longcomplex, longdouble and longfloat. These need to be converted to their nearest NumPy equivalent before using .item().
If you want to convert (numpy.array OR numpy scalar OR native type OR numpy.darray) TO native type you can simply do :
converted_value = getattr(value, "tolist", lambda: value)()
tolist will convert your scalar or array to python native type. The default lambda function takes care of the case where value is already native.
Given a variable in python of type int, e.g.
z = 50 type(z) ## outputs <class 'int'>
is there a straightforward way to convert this variable into numpy.int64?
It appears one would have to convert this variable into a numpy array, and then convert this into int64. That feels quite convoluted.
https://docs.scipy.org/doc/numpy-1.13.0/user/basics.types.html
Use .astype.
>>> a = numpy.array([1, 2, 3, 4], dtype=numpy.float64)
>>> a
array([ 1., 2., 3., 4.])
>>> a.astype(numpy.int64)
array([1, 2, 3, 4])
See the documentation for more options.
While astype is probably the "best" option there are several other ways to convert it to an integer array. I'm using this arr in the following examples:
>>> import numpy as np
>>> arr = np.array([1,2,3,4], dtype=float)
>>> arr
array([ 1., 2., 3., 4.])
The int* functions from NumPy
>>> np.int64(arr)
array([1, 2, 3, 4])
>>> np.int_(arr)
array([1, 2, 3, 4])
The NumPy *array functions themselves:
>>> np.array(arr, dtype=int)
array([1, 2, 3, 4])
>>> np.asarray(arr, dtype=int)
array([1, 2, 3, 4])
>>> np.asanyarray(arr, dtype=int)
array([1, 2, 3, 4])
The astype method (that was already mentioned but for completeness sake):
>>> arr.astype(int)
array([1, 2, 3, 4])
Note that passing int as dtype to astype or array will default to a default integer type that depends on your platform. For example on Windows it will be int32, on 64bit Linux with 64bit Python it's int64. If you need a specific integer type and want to avoid the platform "ambiguity" you should use the corresponding NumPy types like np.int32 or np.int64.