列表中删除数据遇到的两个问题

删除列表中所有小于60的数字

问题1: 通过元素删除的时候可能出现删不干净的问题

scores = [10, 50, 90, 89, 45, 70]
for score in scores:
    if score < 60:
        scores.remove(score)

print(scores, score)    # [50, 90, 89, 20, 70]

"""
scores = [10, 50, 90, 89, 45, 70]
score = 10   if 10 < 60    scores.remove(10)       scores = [50, 90, 89, 45, 70]  
score = 90   if 90 < 60
score = 89   if 89 < 60
score = 45   if 45 < 60    scores.remove(45)       scores = [50, 90, 89, 70] 
"""

解决问题1：

scores = [10, 50, 90, 89, 45, 70]
scores2 = scores[:]
for score in scores2:
    if score < 60:
        scores.remove(score)
del scores2    # score2只是提供遍历用的，用完后没有其他用处，可以直接删除
print(scores, score)

上面的简写

scores = [10, 50, 90, 89, 45, 70]
for score in scores[:]:
    if score < 60:
        scores.remove(score)
print(scores, score)

"""
scores = [10, 50, 90, 89, 45, 70]
scores2 = [10, 50, 90, 89, 45, 70]
score = 10   if 10<60  scores.remove(10)   scores = [50, 90, 89, 45, 70]
score = 50   if 50<60  scores.remove(50)   scores = [90, 89, 45, 70]
score = 90   if 90<60
score = 89   if 89<60
score = 45   if 45<60  scores.remove(45)   scores = [90, 89,70]
score = 70   if 70<60
"""

问题2：通过下标删除满足要求的元素的时候，出现下标越界的错误

print('====================问题2=====================')
scores = [10, 50, 90, 89, 45, 70]
for index in range(len(scores)):
    if scores[index] < 60:
        del scores[index]

print(scores)
"""
scores = [10, 50, 90, 89, 45, 70]
for index in range(6)  
index = range(6)  index = (0,1,2,3,4,5)
index = 0   if scores[0]<60   if 10<60   del scores[0]  scores = [50, 90, 89, 45, 70]
index = 1   if scores[1]<60   if 90<60   
index = 2   if scores[2]<60   if 89<60
index = 3   if scores[3]<60   if 45<60   del scores[3]  scores = [50, 90, 89, 70]
index = 4   if scores[4]<60  (out of range)
"""

解决问题2:

scores = [10, 50, 90, 89, 45, 70]
index = 0
while index < len(scores):
    if scores[index] < 60:
        del scores[index]
        continue
    index += 1

print(scores)
"""
scores = [10, 50, 90, 89, 45, 70]   
index = 0
while 0 < 6    if 10<60   del scores[0]   scores = [50, 90, 89, 45, 70] 
while 0 < 5    if 50<60   del scores[0]   scores = [90, 89, 45, 70]
while 0 < 4    if 90<60   index += 1  index = 1
while 1 < 4    if 89<60   index += 1  index = 2
while 2 < 4    if 45<60   del scores[2]   scores = [90, 89,70]
while 2 < 3    if 70<60   index += 1  index = 3  
while 3 < 3 
print(scores)  -  [90, 89,70] 
"""