A[A==NDV]=numpy.nan
A==NDV will produce a boolean array that can be used as an index for A
Answer from Paul on Stack OverflowAskPython
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Understanding np.nan in NumPy and Pandas - AskPython
September 30, 2026 - Use the mask to select, replace or count those entries. NumPy documents the same rule in its missing-value guidance, which recommends isnan instead of equality. NaN propagates through ordinary arithmetic because the result depends on a value that is unknown.
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Is np.nan a float?
Yes. np.nan is a floating-point value, so including it in a NumPy array of integers causes the array to use a floating-point dtype.
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Understanding np.nan in NumPy and Pandas - AskPython
Should I use np.isnan or pandas isna?
Use np.isnan for numeric NumPy values. Use pandas isna or a Series or DataFrame isna method when the data may contain pandas missing markers, None or NaT.
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Understanding np.nan in NumPy and Pandas - AskPython
What does np.nan do?
np.nan is a floating-point NaN value used to mark an unavailable numeric entry. Use np.isnan to detect it in a NumPy array.
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Understanding np.nan in NumPy and Pandas - AskPython
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numpy.nan | Interactive Chaos
January 16, 2021 - Python scenarios ยท Full name ยท numpy.nan ยท Library ยท NumPy ยท Syntax ยท numpy.nan ยท Description ยท numpy.nan is a special value from the NumPy library that represents the null value. Parameters ยท numpy.nan does not accept arguments. Result ยท numpy.nan returns a value of type float.
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numpy.isnan โ NumPy v2.1 Manual
>>> import numpy as np >>> np.isnan(np.nan) True >>> np.isnan(np.inf) False >>> np.isnan([np.log(-1.),1.,np.log(0)]) array([ True, False, False])
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Miscellaneous โ NumPy v2.5 Manual
>>> myarr = np.array([1., 0., np.nan, 3.]) >>> np.nonzero(myarr == np.nan) (array([], dtype=int64),)
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A[A==NDV]=numpy.nan
A==NDV will produce a boolean array that can be used as an index for A
2 of 2
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You can also use np.where to replace a number with NaN.
arr = np.where(arr==NDV, np.nan, arr)
For example, the following result can be obtained via
arr = np.array([[1, 1, 2], [2, 0, 1]])
arr = np.where(arr==1, np.nan, arr)

This creates a new copy (unlike A[A==NDV]=np.nan) but in some cases that could be useful. For example, if the array was initially an int dtype, it will have to converted into a float array anyway (because replacing values with NaN won't work otherwise) and np.where can handle that.
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Constants โ NumPy v2.5 Manual
>>> import numpy as np >>> np.nan nan >>> np.log(-1) np.float64(nan) >>> np.log([-1, 1, 2]) array([ nan, 0.
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numpy.nan_to_num โ NumPy v2.1 Manual
Replace NaN with zero and infinity with large finite numbers (default behaviour) or with the numbers defined by the user using the nan, posinf and/or neginf keywords.
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numpy.nan_to_num โ NumPy v2.5 Manual
Replace NaN with zero and infinity with large finite numbers (default behaviour) or with the numbers defined by the user using the nan, posinf and/or neginf keywords.
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Python NaN: 4 Ways to Check for Missing Values in Python | DataCamp
February 15, 2024 - This article aims to equip you ... the approach largely depends on the data structure you're working with. NumPy's isnan() function is ideal for identifying NaNs in numeric arrays or single values, offering a straightforward and efficient solution....
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numpy.nan_to_num โ NumPy v2.2 Manual
Replace NaN with zero and infinity with large finite numbers (default behaviour) or with the numbers defined by the user using the nan, posinf and/or neginf keywords.
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NumPy: Functions ignoring NaN (np.nansum, np.nanmean, etc.) | note.nkmk.me
January 23, 2024 - In NumPy, functions like np.sum() and np.mean() return NaN if the array (ndarray) contains any NaN values. To perform calculations that ignore NaN, use functions such as np.nansum() and np.nanmean(). ... For basics on handling NaN in Python, ...