ValueError: could not convert string to float

[badju]

I am trying to convert an entire column (actually, three) to float, but there's something getting wrong.

This is the code:

series = df['time']
mydata = df[['points','lat','lon','t_mn']].apply(lambda x: x.str.replace(',', '.').astype(float), axis=1)
mydata2 = df[['lat','lon','t_mn']].apply(lambda x: x.str.replace(',', '.').astype(float), axis=1)

The Traceback I get is this:

Error:
Traceback (most recent call last):
<ipython-input-39-f787414b7182> in <module>()
if copy or is_object_dtype(arr) or is_object_dtype(dtype):
# Explicit copy, or required since NumPy can't view from / to object.
return arr.astype(dtype, copy=True)

return arr.view(dtype)

ValueError: could not convert string to float:

Output:
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 79 entries, 0 to 78
Data columns (total 5 columns):
 #   Column  Non-Null Count  Dtype 
---  ------  --------------  ----- 
 0   points  79 non-null     int64 
 1   time    79 non-null     int64 
 2   lat     79 non-null     object
 3   lon     79 non-null     object
 4   t_mn    79 non-null     object
dtypes: int64(2), object(3)
memory usage: 3.2+ KB

I already tried to do step by step, replacing the commas first and then trying to change to float, but I am still unsuccessful. I don't know if there is an error in my data, but it looks normal.