TypeError only length-1 arrays can be converted to Python scalars while plot showing

Question

I have such Python code   import numpy as np import matplotlib pyplot as plt  def f x       return np int x   x   np arange 1  15 1  0 1  plt plot x  f x   plt show     And such error   TypeError  only length-1 arrays can be converted to Python scalars   How can I fix it

User · Answer

Use    x astype int    Here is the reference

User · Answer

The error  quot only length-1 arrays can be converted to Python scalars quot  is raised when the function expects a single value but you pass an array instead  If you look at the call signature of np int  you ll see that it accepts a single value  not an array  In general  if you want to apply a function that accepts a single element to every element in an array  you can use np vectorize  import numpy as np import matplotlib pyplot as plt  def f x       return np int x  f2   np vectorize f  x   np arange 1  15 1  0 1  plt plot x  f2 x   plt show    You can skip the definition of f x  and just pass np int to the vectorize function  f2   np vectorize np int   Note that np vectorize is just a convenience function and basically a for loop  That will be inefficient over large arrays  Whenever you have the possibility  use truly vectorized functions or methods  like astype int  as  FFT suggests

User · Answer

Take note of what is printed for x  You are trying to convert an array  basically just a list  into an int  length-1 would be an array of a single number  which I assume numpy just treats as a float  You could do this  but it s not a purely-numpy solution   EDIT  I was involved in a post a couple of weeks back where numpy was slower an operation than I had expected and I realised I had fallen into a default mindset that numpy was always the way to go for speed  Since my answer was not as clean as ayhan s  I thought I d use this space to show that this is another such instance to illustrate that vectorize is around 10  slower than building a list in Python  I don t know enough about numpy to explain why this is the case but perhaps someone else does    import numpy as np import matplotlib pyplot as plt import datetime  time start   datetime datetime now      My original answer def f x       rebuilt to plot          for num in x          rebuilt to plot append np int num       return rebuilt to plot  for t in range 10000       x   np arange 1  15 1  0 1      plt plot x  f x    time end   datetime datetime now      Answer by ayhan def f 1 x       return np int x   for t in range 10000       f2   np vectorize f 1      x   np arange 1  15 1  0 1      plt plot x  f2 x    time end 2   datetime datetime now    print time end - time start print time end 2 - time end

User · Answer

dataframe  column   squeeze   should solve this  It basically changes the dataframe column to a list

[python] TypeError: only length-1 arrays can be converted to Python scalars while plot showing

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