xirr：TypeError：“ float”对象不可调用

Question

我有一个带有日期，现金，名称，密钥列的数据框。我正在尝试通过对密钥进行分组来找到xirr。但是，当我运行代码时，出现错误“ TypeError：'float'对象不可调用”

f1['l'] = list(zip(f1["Date"], f1["Cash"]))
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def xirr(transactions):
    years = [(ta[0] - transactions[0][0]).days / 365.0 for ta in transactions]
    residual = 1
    step = 0.05
    guess = 0.05
    epsilon = 0.0001
    limit = 10000
    while abs(residual) > epsilon and limit > 0:
        limit -= 1
        residual = 0.0
        for i, ta in enumerate(transactions):
            residual += ta[1] / pow(guess, years[i])
        if abs(residual) > epsilon:
            if residual > 0:
                guess += step
            else:
                guess -= step
                step /= 2.0
    return guess-1

print(xirr(f1['l'])) #till here it runs  
f2 = f1.groupby('KEY').apply(xirr(f1['l']))  # this line is giving error