Fail to convert float 64 to float 32 in python

I tried to convert the data from data type float 64 to float 32. I used both pandas method and pytorch but no avail. Dataset are from kaggle titanic project. The code is the following:

from torch import nn
import torch
import pandas as pd
import numpy as np
df = pd.DataFrame([[1.1, 2.1], [3.1, 4.1],[5.1,6.1]], columns=['col1', 'col2'])
df.astype('float32')
print(df.dtypes)
df.astype(np.float32)
print(df.dtypes)
a=torch.tensor(df.loc[1][['col1']])
a.to(torch.float32)
print(a)

and get the result

col1    float64
col2    float64
dtype: object
col1    float64
col2    float64
dtype: object
tensor([3.1000], dtype=torch.float64)

I tried to use both method provided by pandas and pytorch. Although it does not raise any errors, it does not work. And I cannot put it into neural network layers as it requires float 32 data type. I also tried to convert them to int, int64, int32 using both method. But nothing works.

Solution

Code

Check out the announcements and make sure to ask questions with minimal and reproducible example. It's harder to get answers if we have to read your long code without a reproducible sample.

minimal and reproducible example:

import pandas as pd
df = pd.DataFrame([[1.1, 2.1], [3.1, 4.1]], columns=['col1', 'col2'])

df:

   col1  col2
0   1.1   2.1
1   3.1   4.1

chk dtype of df

print(df.dtypes)

print:

col1    float64
col2    float64
dtype: object

convert to float32

out = df.astype('float32')
print(out.dtypes)

orint:

col1    float32
col2    float32
dtype: object

Most functions in Pandas do not change the original as a result of applying the function.