使用with打開文件的好處不多說凿叠，這里記錄一下如果要打開多個(gè)文件厘擂，該怎么書寫簡捷的代碼昆淡。
場景是同時(shí)打開三個(gè)文件，文件行數(shù)一樣刽严，程序?qū)崿F(xiàn)每個(gè)文件依次讀取一行昂灵，同時(shí)輸出。 首先來一種比較容易想到的寫法，如下一樣嵌套：
with open('file1') as f1:
with open('file2') as f2:
with open('file3') as f3:
for i in f1:
j = f2.readline()
k = f3.readline()
print(i,j,k)
注意倔既，這里只能對一個(gè)文件進(jìn)行for循環(huán)讀取恕曲，不能寫成：
for i,j,k in f1,f2,f3:
print(i,j,k)
這么多層縮進(jìn)太惡心了，還是來一種簡潔些的寫法：
with open('file1') as f1, open('file2') as f2, open('file3') as f3:
for i in f1:
j = f2.readline()
k = f3.readline()
print(i,j,k)
還有一種優(yōu)雅一點(diǎn)的寫法：
from contextlib import nested
with nested(open('file1'), open('file2'), open('file3')) as (f1,f2,f3):
for i in f1:
j = f2.readline()
k = f3.readline()
print(i,j,k)
