Panda Python error: could not convert string to float

Question

I can not change my string to float value. Im new at Python and could not find any similar issues on stack overflow. Sorry if I have missed it...

Snippet of my data.

My code looks like this

  import pandas as pd
  import numpy as np
  data = pd.read_csv('data.csv')

dt = data.rename(columns = {"Unnamed: 0": "test", "Unnamed: 1": "name", "Unnamed: 2": "week"})

dt.dtypes

Output

test           object
name           object
week           object
Total          object
§83            object
§83.1          object
Unnamed: 6     object
Unnamed: 7     object
Unnamed: 8     object
Unnamed: 9     object
Unnamed: 10    object
§83.2          object
Unnamed: 12    object
Unnamed: 13    object
Unnamed: 14    object
Unnamed: 15    object
Unnamed: 16    object
§83a           object
Unnamed: 18    object
Unnamed: 19    object
Unnamed: 20    object
Unnamed: 21    object
Unnamed: 22    object
dtype: object

Want to change my string in Col Total to float with this

dt.Total = dt.Total.astype(float)

Error: ValueError: could not convert string to float: 'Total' See below for total info

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-78-ad6ed6a5e004> in <module>
----> 1 dt.Total = dt.Total.astype(float)

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/generic.py in astype(self, dtype, copy, errors)
   5546         else:
   5547             # else, only a single dtype is given
-> 5548             new_data = self._mgr.astype(dtype=dtype, copy=copy, errors=errors,)
   5549             return self._constructor(new_data).__finalize__(self, method="astype")
   5550 

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/internals/managers.py in astype(self, dtype, copy, errors)
    602         self, dtype, copy: bool = False, errors: str = "raise"
    603     ) -> "BlockManager":
--> 604         return self.apply("astype", dtype=dtype, copy=copy, errors=errors)
    605 
    606     def convert(

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/internals/managers.py in apply(self, f, align_keys, **kwargs)
    407                 applied = b.apply(f, **kwargs)
    408             else:
--> 409                 applied = getattr(b, f)(**kwargs)
    410             result_blocks = _extend_blocks(applied, result_blocks)
    411 

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/internals/blocks.py in astype(self, dtype, copy, errors)
    593             vals1d = values.ravel()
    594             try:
--> 595                 values = astype_nansafe(vals1d, dtype, copy=True)
    596             except (ValueError, TypeError):
    597                 # e.g. astype_nansafe can fail on object-dtype of strings

/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pandas/core/dtypes/cast.py in astype_nansafe(arr, dtype, copy, skipna)
    995     if copy or is_object_dtype(arr) or is_object_dtype(dtype):
    996         # Explicit copy, or required since NumPy can't view from / to object.
--> 997         return arr.astype(dtype, copy=True)
    998 
    999     return arr.view(dtype)

ValueError: could not convert string to float: 'Total'

UPDATED:

Answer 1

If any of your columns contain a string value (even an alphabet for that matter), python will show an error while trying to convert it to float or int. The first two rows of the TOTAL column are strings. For this reason, you might want to remove these or replace them with some other suitable values before attempting to convert the column values to float.