How to calculate the number of variables in the smali file during decompilation

Question

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def parse_smali_field_num(smali_path):
    count = 0
    with open(smali_path, 'r', 4096, 'utf-8') as f:
        text = f.readline()
        if (not text.startswith('.class')):
            print('Warning:Not a class smali file:' + str(smali_path))
            return 0
        while (text):
            text = f.readline()
            if (text.startswith('.field')):
                count += 1
    return count