1.代码实现

s = "python"
while s != "":
    print(s)
    for c in s:
        if c == "t": #打印出t之前的字母
            break
        print(c,end='') #不换行，直到break结束
    s = s[:-1] # 逐个减一
    print()

2.运行结果

python
py
pytho
py
pyth
py
pyt
py
py
py
p
p