Python several ways to read the file line by line

Python four kinds of content to read the file line by line method

The following four Python file content read line by line method to analyze the advantages and disadvantages of various methods of application scenarios, the following code in python3 tested by, python2 running part of the code annotated, slightly modified.

Method a: readline function

# -*- coding: UTF-8 -*-
f = open("/pythontab/code.txt")  # 返回一个文件对象
line = f.readline()  # 调用文件的 readline()方法
while line:
    # print line,      # 在 Python 2中，后面跟 ',' 将忽略换行符
    print(line, end='')  # 在 Python 3中使用
    line = f.readline()
f.close()

Advantages: save memory, do not need to file a one-time content into memory.
Disadvantages: relatively slow.

Method two: a multi-line data read

代码如下:
# -*- coding: UTF-8 -*-
f = open("/pythontab/code.txt")
while 1:
    lines = f.readlines(10000)
    if not lines:
        break
    for line in lines:
        print(line)
f.close()

Multi-line one-time reading, can improve the reading speed, but slightly larger memory use, the first reading may be adjusted according to the number of rows where

Method three: Direct for loop

Cycle time can be used for each row of data directly to a file object, as follows:

# -*- coding: UTF-8 -*-
for line in open("/pythontab/code.txt"):
    # print line,  #python2 用法
    print(line)

Method 4: Use fileinput module

import fileinput
for line in fileinput.input("/pythontab/code.txt"):
    print(line)

Simple to use, but slower

Reprinted from: https: //www.jianshu.com/p/4658e3ed1fea