convert.py

def str_to_interval(text: str):
    if isinstance(text, str):
        years = text.split()[0].split("-")
        if len(years) == 2:
            return pd.Interval(int(years[0]), int(years[1]))
        else:
            return pd.Interval(int(years[0]), float("inf"))

    return text

# Convert string to pandas.Interval    
normal_salary.YearsCoding = normal_salary.YearsCoding.apply(str_to_interval)

# Sort by years
years_sorted = normal_salary.dropna(
    subset=["ConvertedSalary", "YearsCoding"]
).sort_values(by="YearsCoding")