pandas string to float missing value

Question

I want to convert 'string' to 'float' in dataframe but when I convert '123.32346236574' to float using astype(float) the result is only display x.xxxxxx ,missing value...! how to convert string to float without mssing data?

and test the code... why display result this way? code

df = pd.DataFrame(['s', -129342.4298429842])
print(df)

result

                             0
0                            s
1 -129342.42984298420196864754