How to extract a single word from a text file

[buttercup]

Hey all. I have a test file called beta.txt which has the following data:
ARFCN: 990, Freq: 928.2M, CID: 667, LAC: 1007, MCC: 410, MNC: 3, Pwr: -30

I wish to save the value of frequency in a variable such that whenever I run the following command:

grgsm_livemon_headless -f 944.2M

The value of the frequency stored in the variable is placed in place of 944.2M.

The values of the variable may change after ever while and I want to generate a code that can keep on automatically updating the value.

Ive tried initially by reading the test file and then splitting it.

beta = open('beta.txt', 'rt')
betalines = beta.readlines()
x = print(betalines)
y = x.split()
print(y)

However this always returns the following error:

Error:
['ARFCN:  990, Freq:  928.2M, CID:   667, LAC:  1007, MCC: 410, MNC:   3, Pwr: -27\n']
Traceback (most recent call last):
  File "example.py", line 34, in <module>
    y = x.split()
AttributeError: 'NoneType' object has no attribute 'split'

I then also tried to store the line in a variable but that is not working either.

mylines = []
with open ('beta.txt', 'rt') as myfile:
	for myline in myfile:
		mylines.append(myline)
print(mylines)

The list of individual words in the test file can be made by using the following code:

with open('beta.txt','r') as f:          
	for line in f:
		for word in line.split():
			print(word)

But I dont know how to proceed further so that the second word of the list is always stored in a variable, say x, and that value of x can be added in the headless livemon formula.
Thanks