pd.read_csv dtype error when there is str"inf" in the float column 
#### A small, complete example of the issue
pd.read_csv  dtype error when there is string "inf" in one column of the csv file. 

part file detail:
31    1.159451e+261
32    8.804630e+291
33    1.355031e+293
34    2.288852e+303
35              inf
36    4.439159e+261
37    1.809108e+282
38    2.257864e+250
39    8.623610e+295
Name: FT64, dtype: float64

df = pd.read_csv(src_path+os.sep+file, dtype=float) :  will be **error**

but when i use this code :+1:  df = pd.read_csv(src_path+os.sep+file), the csv can be read in. and
the element type is object(str).  i can use df.astype(float) to convert the df. 

i am just confusing why use read_csv(file, dtype=float)  is not useful
