python - 如何遍历python中的列表列表

Question

需要遍历列表列表并测试字符串是黑色还是红色，然后从列表中的浮点数中添加或减去 - 例如，如果“黑色”则加 1，如果字符串值为“红色”，则减 1

new_line = [["Black", 3.0], ["Red", 7.0], ["Red", 2.0], ["Black", 3.5]]

for i in new line:
    if value == "Black":
          add =+ 1 to float value (3.0 in first example)
    else: 
          subtract -=1 float value (7.0 in second value n list)

标签： pythonloopsnested

Answer 1

这应该工作

new_line = [["Black", 3.0], ["Red", 7.0], ["Red", 2.0], ["Black", 3.5]]

for i in new_line:
     if i[0] == "Black":
          i[1] += 1.0
     else: 
          i[1] -= 1.0

 print(new_line)