Python 文件操作

f = open(‘somefile.txt‘) # 文件名是唯一必不可少的参数，返还一个文件对象

f = open(‘somefile.txt‘, ‘w‘)
f.write(‘Hello, ‘)
f.write(‘World!‘)
f.close()

f = open(‘somefile.txt‘, ‘r‘)
f.read(4)#读取4个字符
f.read()#读取剩下的所有内容

#somescript.py
import sys
text = sys.stdin.read() #读取stdin中的所有内容
words = text.split() #将stdin中的所有内容分割成words
wordcount = len(words)
print(‘Wordcount:‘, wordcount)

#readline
f = open(r‘C:\text\somefile.txt‘)
for i in range(3):
    print(str(i) + ‘: ‘ + f.readline(), end = ‘ ‘)
#结果：
#0: Welcome to this file
#1: There is nothing here except
#2: This stupid haiku
f.close()

#readlines():
import pprint # pprint 之前没有接触过
pprint.pprint(open(r‘C:\text\somefile.txt‘).readlines())
#结果：
#[‘Welcome to this file\n‘,
#‘There is nothing here except\n‘,
#‘This stupid haiku‘]

#writelines():
f = open(r‘C:\text\somefile.txt‘)
lines = f.readlines()
f.close()
line[1] = "isn‘t a\n"
f = open(r‘C:\text\somefile.txt‘, ‘w‘ )
f.writelines(lines)
f.close()

with open(filename) as f : # 上下文管理器，结束后自动关闭文件
    while True:
        line = f.readline()
        if not line: break
        process(line) # process函数是自己写的，示例中作者写的process功能是输出line到 stdout

#fileinput: 只读取需要的部分，适用于很大的文件（无法一次读出所有内容）
import fileinput
for line in fileinput.input(filename):
    process(line)

with open(filename) as f:
    for line in f:
        proccess(line)

for line in open(filename):
    process(line)

import sys #迭代标准输入内容
for line in sys.stdin:
    process(line)