python TypeError使用sys.stdout.write作为数组元素值

Question

我有一个Python中的print语句，它显示数组中元素的值和长度。 然后我需要使用sys.stdout.write而不是打印来做同样的事情，但是我得到了下面的错误

使用打印的原始代码：

import sys
words = ["Madagascar", "Russia", "Antarctica", "Tibet", "Mongolia"]
for w in words:
    print(w, len(w))

将打印替换为sys.stdout.write：

import sys
countries = ["Madagascar", "Russia", "Antarctica", "Tibet", "Mongolia"]
for w in countries:
    sys.stdout.write(countries[w]+" "+len(countries[w]))

我得到的错误是：

Traceback (most recent call last):
    File "/Users/m/loop.py", line 5, in <module>
    sys.stdout.write(countries[w]+" "+len(countries[w]))
TypeError: list indices must be integers or slices, not str

Answer 1

在这样的for循环中，循环变量从列表中获取值，而不是其索引。换句话说，不是每个国家的指数，而是国家本身。 此外，请注意，不能像这样连接字符串和int，因此必须将len的结果也转换为字符串：

from sys import stdout
countries = ["Madagascar", "Russia", "Antarctica", "Tibet", "Mongolia"] # corrected spelling error Antartica -> Antarctica
for w in countries:
    stdout.write(f"{w} {len(w)}\n") # \n otherwise output will be in the same line (sys.stdout.write ISN'T print which adds \n by default at the end of line.

较短版本

from sys import stdout
countries = ["Madagascar", "Russia", "Antarctica", "Tibet", "Mongolia"]
[stdout.write(f"{w} {len(w)}\n") for w in countries] # [] are important and for Python 2 compatibility (and some IDEs and REPLs don't support f-strings) you can use **"%s %d" % (w, len(w))** instead of **f"{w} {len(w)}"**