前言

用python 读取一个大于10G 的文件，自己电脑只有8G内存，一运行就报内存溢出：MemoryError

python 如何用open函数读取大文件呢？

读取大文件

首先可以自己先制作一个大于10G的txt文件

a = '''

2021-02-02 21:33:31,678 [django.request:93] [base:get_response] [WARNING]- Not Found: /http:/123.125.114.144/

2021-02-02 21:33:31,679 [django.server:124] [basehttp:log_message] [WARNING]- "HEAD http://123.125.114.144/ HTTP/1.1" 404 1678

2021-02-02 22:14:04,121 [django.server:124] [basehttp:log_message] [INFO]- code 400, message Bad request version ('HTTP')

2021-02-02 22:14:04,122 [django.server:124] [basehttp:log_message] [WARNING]- "GET ../../mnt/custom/ProductDefinition HTTP" 400 -

2021-02-02 22:16:21,052 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login HTTP/1.1" 301 0

2021-02-02 22:16:21,123 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login/ HTTP/1.1" 200 3876

2021-02-02 22:16:21,192 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/img/main_bg.png HTTP/1.1" 200 2801

2021-02-02 22:16:21,196 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/style.css HTTP/1.1" 200 1638

2021-02-02 22:16:21,229 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/img/bg.jpg HTTP/1.1" 200 135990

2021-02-02 22:16:21,307 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/fonts/icomoon.ttf?u4m6fy HTTP/1.1" 200 6900

2021-02-02 22:16:23,525 [django.server:124] [basehttp:log_message] [INFO]- "POST /api/login/ HTTP/1.1" 302 0

2021-02-02 22:16:23,618 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/index/ HTTP/1.1" 200 18447

2021-02-02 22:16:23,709 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/commons.js HTTP/1.1" 200 13209

2021-02-02 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/admin.css HTTP/1.1" 200 19660

2021-02-02 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/common.css HTTP/1.1" 200 1004

2021-02-02 22:16:23,714 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/app.js HTTP/1.1" 200 20844

2021-02-02 22:16:26,509 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/report_list/1/ HTTP/1.1" 200 14649

2021-02-02 22:16:51,496 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/test_list/1/ HTTP/1.1" 200 24874

2021-02-02 22:16:51,721 [django.server:124] [basehttp:log_message] [INFO]- "POST /api/add_case/ HTTP/1.1" 200 0

2021-02-02 22:16:59,707 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/test_list/1/ HTTP/1.1" 200 24874

2021-02-03 22:16:59,909 [django.server:124] [basehttp:log_message] [INFO]- "POST /api/add_case/ HTTP/1.1" 200 0

2021-02-03 22:17:01,306 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/edit_case/1/ HTTP/1.1" 200 36504

2021-02-03 22:17:06,265 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/add_project/ HTTP/1.1" 200 17737

2021-02-03 22:17:07,825 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/project_list/1/ HTTP/1.1" 200 29789

2021-02-03 22:17:13,116 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/add_config/ HTTP/1.1" 200 24816

2021-02-03 22:17:19,671 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/config_list/1/ HTTP/1.1" 200 19532

'''

while True:

    with open("xxx.log", "a", encoding="utf-8") as fp:

         fp.write(a)

循环写入到 xxx.log 文件，运行 3-5 分钟，pycharm 打开查看文件大小大于 10G

于是我用open函数直接读取

f = open("xxx.log", 'r')

print(f.read())

f.close()

抛出内存溢出异常:MemoryError

Traceback (most recent call last):

  File "D:/2021kecheng06/demo/txt.py", line 35, in <module>

    print(f.read())

MemoryError

运行的时候可以看下自己电脑的内存已经占了100%， cpu高达91% ，不挂掉才怪了！

这种错误的原因在于，read()方法执行操作是一次性的都读入内存中，显然文件大于内存就会报错。

read() 的几种方法

1.read() 方法可以带参数 n， n 是每次读取的大小长度，也就是可以每次读一部分，这样就不会导致内存溢出

f = open("xxx.log", 'r')

print(f.read(2048))

f.close()

运行结果

2019-10-24 21:33:31,678 [django.request:93] [base:get_response] [WARNING]- Not Found: /http:/123.125.114.144/

2019-10-24 21:33:31,679 [django.server:124] [basehttp:log_message] [WARNING]- "HEAD http://123.125.114.144/ HTTP/1.1" 404 1678

2019-10-24 22:14:04,121 [django.server:124] [basehttp:log_message] [INFO]- code 400, message Bad request version ('HTTP')

2019-10-24 22:14:04,122 [django.server:124] [basehttp:log_message] [WARNING]- "GET ../../mnt/custom/ProductDefinition HTTP" 400 -

2019-10-24 22:16:21,052 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login HTTP/1.1" 301 0

2019-10-24 22:16:21,123 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login/ HTTP/1.1" 200 3876

2019-10-24 22:16:21,192 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/img/main_bg.png HTTP/1.1" 200 2801

2019-10-24 22:16:21,196 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/style.css HTTP/1.1" 200 1638

2019-10-24 22:16:21,229 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/img/bg.jpg HTTP/1.1" 200 135990

2019-10-24 22:16:21,307 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/fonts/icomoon.ttf?u4m6fy HTTP/1.1" 200 6900

2019-10-24 22:16:23,525 [django.server:124] [basehttp:log_message] [INFO]- "POST /api/login/ HTTP/1.1" 302 0

2019-10-24 22:16:23,618 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/index/ HTTP/1.1" 200 18447

2019-10-24 22:16:23,709 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/commons.js HTTP/1.1" 200 13209

2019-10-24 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/admin.css HTTP/1.1" 200 19660

2019-10-24 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/common.css HTTP/1.1" 200 1004

2019-10-24 22:16:23,714 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/app.js HTTP/1.1" 200 20844

2019-10-24 22:16:26,509 [django.server:124] [basehttp:log_message] [I

这样就只读取了2048个字符，全部读取的话，循环读就行

f = open("xxx.log", 'r')

while True:

    block = f.read(2048)

    print(block)

    if not block:

        break

f.close()

2.readline()：每次读取一行，这个方法也不会报错

f = open("xxx.log", 'r')

while True:

    line = f.readline()

    print(line, end="")

    if not line:

        break

f.close()

readlines()：读取全部的行，生成一个list，通过list来对文件进行处理，显然这种方式依然会造成：MemoyError

真正 Pythonic 的方法

真正 Pythonci 的方法，使用 with 结构打开文件，fp 是一个可迭代对象，可以用 for 遍历读取每行的文件内容

with open("xxx.log", 'r') as fp:

    for line in fp:

        print(line, end="")

yield 生成器读取大文件

前面一篇讲yield 生成器的时候提到读取大文件，函数返回一个可迭代对象，用next()方法读取文件内容

def read_file(fpath):

    BLOCK_SIZE = 1024

    with open(fpath, 'rb') as f:

        while True:

            block = f.read(BLOCK_SIZE)

            if block:

                yield block

            else:

                return

if __name__ == '__main__':

    a = read_file("xxx.log")

    print(a)            # generator objec

    print(next(a))      # bytes类型

    print(next(a).decode("utf-8"))   # str

运行结果

<generator object read_file at 0x00000226B3005258>

b'\r\n2019-10-24 21:33:31,678 [django.request:93] [base:get_response] [WARNING]- Not Found: /http:/123.125.114.144/\r\n2019-10-24 21:33:31,679 [django.server:124] [basehttp:log_message] [WARNING]- "HEAD http://123.125.114.144/ HTTP/1.1" 404 1678\r\n2019-10-24 22:14:04,121 [django.server:124] [basehttp:log_message] [INFO]- code 400, message Bad request version (\'HTTP\')\r\n2019-10-24 22:14:04,122 [django.server:124] [basehttp:log_message] [WARNING]- "GET ../../mnt/custom/ProductDefinition HTTP" 400 -\r\n2019-10-24 22:16:21,052 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login HTTP/1.1" 301 0\r\n2019-10-24 22:16:21,123 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/login/ HTTP/1.1" 200 3876\r\n2019-10-24 22:16:21,192 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/img/main_bg.png HTTP/1.1" 200 2801\r\n2019-10-24 22:16:21,196 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/style.css HTTP/1.1" 200 1638\r\n2019-10-24 22:16:21,229 [django.server:124] '

[basehttp:log_message] [INFO]- "GET /static/assets/img/bg.jpg HTTP/1.1" 200 135990

2019-10-24 22:16:21,307 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/iconfont/fonts/icomoon.ttf?u4m6fy HTTP/1.1" 200 6900

2019-10-24 22:16:23,525 [django.server:124] [basehttp:log_message] [INFO]- "POST /api/login/ HTTP/1.1" 302 0

2019-10-24 22:16:23,618 [django.server:124] [basehttp:log_message] [INFO]- "GET /api/index/ HTTP/1.1" 200 18447

2019-10-24 22:16:23,709 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/commons.js HTTP/1.1" 200 13209

2019-10-24 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/admin.css HTTP/1.1" 200 19660

2019-10-24 22:16:23,712 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/css/common.css HTTP/1.1" 200 1004

2019-10-24 22:16:23,714 [django.server:124] [basehttp:log_message] [INFO]- "GET /static/assets/js/app.js HTTP/1.1" 200 20844

2019-10-24 22:16:26,509 [django.server:124] [basehtt

面试题-python 如何读取一个大于 10G 的txt文件？的更多相关文章

如何用 php 读取一个很大的 excel 文件。
这个程序是用php 读取一个很大的excel文件, 先将 excel 文件保存成csv 文件, 然后利用迭代器逐行读取 excel 单元格的值, 拿到值以后做相应处理,并打印结果. <?p ...
C#读取固定文本格式的txt文件
C#读取固定文本格式的txt文件一个简单的C#读取txt文档的程序,文档中用固定的格式存放着实例数据. //判断关键字在文档中是否存在 ] == "设备ID:107157061" ...
Java读取CSV数据并写入txt文件
读取CSV数据并写入txt文件 package com.vfsd; import java.io.BufferedWriter; import java.io.File; import java.io ...
Python读取一个目录下的所有文件
#!/usr/bin/python # -*- coding:utf8 -*- import os allFileNum = 0 def printPath(level, path): global ...
Python：遍历一个目录下所有的文件及文件夹，然后计算每个文件的字符和line的小程序
编写了一个遍历一个目录下所有的文件及文件夹,然后计算每个文件的字符和line的小程序,先把程序贴出来. #coding=utf-8 ''' Created on 2014年7月14日 @author: ...
【Python】读取各种文档（txt、csv、excel、pdf）方法
1.读取txt文件注意事项: 1..txt文件同下方脚本所在的.py文件需要在同一个文件夹下 # coding=utf-8 txt读取 with open("1233.txt") ...
matlab读取内容为二进制的TXT文件
本方法同样适合读取十六进制和二进制以外的其他进制文件,txt使用一个最简单的命令就可以读取 textread 这是一个十分有用,简便的函数(对于fopen fscanf而言)读取二进制txt文件:假如 ...
python学习笔记（1）--遍历txt文件，正则匹配替换文字
遍历一个文件夹,把里面所有txt文件里的[]里的朗读时间删除,也就是替换为空. import os import re import shutil #os文件操作,re正则,shutil复制粘贴 pa ...
python的OS模块生成100个txt文件
#!/user/bin/env/python35 # -*-coding:utf-8-*- # author:Keekuun """ 问题:生成一个文件夹,文件夹下面生成 ...

随机推荐

【hdu 4859】海岸线（图论--网络流最小割）
题意:有一个区域,有'.'的陆地,'D'的深海域,'E'的浅海域.其中浅海域可以填充为陆地.这里的陆地区域不联通,并且整个地图都处在海洋之中.问填充一定浅海域之后所有岛屿的最长的海岸线之和. 解法:最 ...
hdu4028 The time of a day (map+dp)
Problem Description There are no days and nights on byte island, so the residents here can hardly de ...
Codeforces Round #296 (Div. 2B. Error Correct System
Ford Prefect got a job as a web developer for a small company that makes towels. His current work ta ...
[POJ 2585] Window Pains 拓朴排序
题意:你现在有9个2*2的窗口在4*4的屏幕上面,由于这9这小窗口叠放顺序不固定,所以在4*4屏幕上有些窗口只会露出来一部分. 如果电脑坏了的话,那么那个屏幕上的各小窗口叠放会出现错误.你的任务就是判 ...
fzu2200 cleaning
Problem Description N个人围成一圈在讨论大扫除的事情,需要选出K个人.但是每个人与他距离为2的人存在矛盾,所以这K个人中任意两个人的距离不能为2,他们想知道共有多少种方法. In ...
Codeforces Round #241 (Div. 2) B. Art Union (DP)
题意:有\(n\)个画家,\(m\)幅画,每个画家负责\(m\)幅画,只有前一个画家画完时,后面一个画家才能接着画,一个画家画完某幅画的任务后,可以开始画下一幅画的任务,问每幅画最后一个任务完成时的时 ...
Explain 索引优化分析
Explain 语法 # 语法 explain + DQL语句 mysql> explain select * from city where countrycode ='CHN' or cou ...
SPOJ REPEATS Repeats （后缀数组 + RMQ：子串的最大循环节）题解
题意: 给定一个串\(s\),\(s\)必有一个最大循环节的连续子串\(ss\),问最大循环次数是多少思路: 我们可以知道,如果一个长度为\(L\)的子串连续出现了两次及以上,那么必然会存在\(s[ ...
Front End Frameworks Trending 2021
Front End Frameworks Trending 2021 Front End Frameworks https://2019.stateofjs.com/front-end-framewo ...
Ant-design-vue—— 表单输入框输入很卡问题
参考:https://blog.csdn.net/weixin_43905402/article/details/106074435 我的问题:vue项目中使用ant-design-vue,表单中输入 ...

面试题-python 如何读取一个大于 10G 的txt文件？