не доработать программку..поменять местами максимальный и минимальный элементы

si=0
ei=0
minnum=matr[si][ei]
for i in range(len(matr)):
    for j in range(len(matr[si])):
        n=matr[si][ei]
        if minnum>n:
            minnum=n
            nr=ei
        
        ei=ei+1
    print(si+1, " rjadu : ",minnum, " ego porjadkovij nomer ", nr+1)

min_si = 0;
min_ei = 0;
 
minnum=matr[si][ei]
for si in range(len(matr)):
    for ei in range(len(matr[si])):
        n=matr[si][ei]
        if minnum>n:
            minnum=n
            min_si = si
            min_ei = ei

matr[max_si][max_ei] = minnum
matr[min_si][min_ei] = maxnum

for row in matr:
    print row

for si in range(len(matr)):
    max_ti = 0;
    min_ei = 0;
    minnum=matr[si][ei]
    maxnum=matr[si][ei] 
        for ei in range(len(matr[si])):
                n=matr[si][ei]
                if minnum > n:
                        minnum=n
                        min_ei = ei
        if maxnum < n:
            maxnum=n
            max_ei = ei
    matr[si][min_ei] = maxnum
    matr[si][max_ei] = minnum

>>> matr
[[1, 2, 3, 4], [-1, -2, 3, 4], [1, 2, 3, 5]]
>>> rows_info = []
>>> for row in matr:
...   low, high = min(row), max(row)
...   rows_info.append(((low, row.index(low)), (high, row.index(high))))
... 
>>> rows_info
[((1, 0), (4, 3)), ((-2, 1), (4, 3)), ((1, 0), (5, 3))]
>>> for row in rows_info:
...   print('min:', row[0], 'max:', row[1])
... 
min: (1, 0) max: (4, 3)
min: (-2, 1) max: (4, 3)
min: (1, 0) max: (5, 3)
>>>