Can't convert string into float in pandas

Question

I'm struggling to my df['High'] into float, I'm not sure what I did wrong or its any other way to convert them. Many thanks in advance.

df.info() details with High, Low, Volume as object type

error codes

It's because you have a `'-'` in that column. You can't convert that to a float because it's obviously not a float. — chitown88, Aug 19 '21 at 11:42
secondly. Don't post pictures of your code, post the actual code. — chitown88, Aug 19 '21 at 11:43
I run the following code to remove '-' df['High'] = df['High'].replace('-','')[0:] but give me the error: ValueError: could not convert string to float: — dynosaur_, Aug 19 '21 at 11:47
No worries, But put that in the original post, not the comments. — chitown88, Aug 19 '21 at 11:49

score 1 · Accepted Answer · answered Aug 19 '21 at 11:48

It's because you have a '-' in that column. Likewise, changing to just empty string of '' will also not convert to float. You can't convert that to a float because it's obviously not a float.

You can replace the '-' with nan

import pandas as pd
import numpy as np

df = pd.DataFrame({'High':['20.1','100.3','99','-']})

df['High'] = df['High'].replace('-', np.nan)
df['High'] = df['High'].astype(float)

Output:

Before:

df.info()
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 4 entries, 0 to 3
Data columns (total 1 columns):
 #   Column  Non-Null Count  Dtype 
---  ------  --------------  ----- 
 0   High    4 non-null      object
dtypes: object(1)
memory usage: 160.0+ bytes

After:

df.info()
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 4 entries, 0 to 3
Data columns (total 1 columns):
 #   Column  Non-Null Count  Dtype  
---  ------  --------------  -----  
 0   High    3 non-null      float64
dtypes: float64(1)
memory usage: 160.0 bytes

Thank you so much! that explains why! cheers for the help. – dynosaur_ Aug 19 '21 at 11:56 — dynosaur_, Aug 19 '21 at 11:56

Can't convert string into float in pandas

1 Answers1