Double for loop

for r in range(4):
    for c in range(6):
        if c % 2 == 0:
            print("*", end="")
        else:
            print("#", end="")
    print()

Outer loop control inner row control column
“”"
0
01
012
0123
“”"
Row fixed as 4 The rows and columns should change with the rows

for r in range(4):
    for c in range(r+1):
        print(c,end="")
    print()

for r in range(4):
    for c in range(r+1):
        print("*",end="")
    print()

Sort the list （ Ascending small –> Big ）

"""  Comparing the two   thought   Take the first one and compare it with the second   Take out the second one and compare it with the three   If the extracted element is larger than the second, the position is exchanged  .... """

list01 = [3, 80, 45, 5, 7, 1]

for r in range(len(list01)-1):
    for c in range(r + 1, len(list01)):

        if list01[r] > list01[c]:
            list01[r], list01[c] = list01[c], list01[r]


print(list01)

"""  Judge that the list elements have the same [3,80,45,5,80,1]  Ideas ： Compare all elements in pairs , If the same one is found, the result will be printed   All element comparisons are over , The same item was not found , Then print the result  """
flag = 1
list01 = [3, 45, 5, 5, 80, 80, 1]
for r in range(len(list01) - 1):
    for c in range(r + 1, len(list01)):
        if list01[r] == list01[c]:
            flag = 0
            print("%d repeated " % list01[r])
            break
    if flag == 0:
        break
else:
    print(" No repeat ")

Matrix transformation turns columns into rows

list01 = [[1, 2, 3, 4],
          [5, 6, 7, 8],
          [9, 10, 11, 12],
          [13, 14, 15, 16]]
list02 = []
for c in range(len(list01[0])):

    list02.append([])
    for r in range(len(list01)):
        list02[c].append(list01[r][c])
print(
    list02
)

"""  List derivation nesting  """
list01=["a","b","c"]
list02=["A","B","C"]
list04 =[ i+j for i in list01 for j in list02]
print(list04)