如何解决这个问题؟索引器错误：字符串索引超出范围

Question

 File "C:/Users/rawaa/raw/New folder/stegano.py", line 398, in show_data
    ch = bedazzle_black(gmaster[f])
IndexError: string index out of range

我的代码：

def show_data(gg_master,fl=flag,key1=bin1):

    if fl == 1:

        bin2 = key1

    else:

        bin2 = bin1

    str_fi = ""

    gmaster = gg_master 

    #print(gmaster)

    first = 0

    last = 0

    for h in range(len(bin2)):

        d1 = bin2[h]

        last = d1[-1]

        if h%2 == 0:

            for f in range(first,last+1):

                if f in d1:

                    ch = bedazzle_green(gmaster[f])

                    str_fi = str_fi + ch

                else :

                    ch = bedazzle_black(gmaster[f])

                    str_fi = str_fi + ch