File(文件) Operation

File Open/Write

用于打开/创建文本, 可执行 读("r")， 写("w")， 加("a") 功能, 默认为("r")

read(), readline(), readlines()

read() - 读全文

readline() - 读每一行

readlines() - 读每一行, 并返回为列表(list)

>>> f=open("newtext.txt", "w")

>>> f.write("hello world!")

• r: Opens the file in read-only mode. Starts reading from the beginning of the file and is the default mode for the open() function.

• wb: Opens a write-only file in binary mode.

• w+: Opens a file for writing and reading.

• a: Opens a file for appending new information to it. The pointer is placed at the end of the file. A new file is created if one with the same name doesn't exist.

File Open/Write with Json

json.dump, json.load

json.dumps, json.loads

Read/Write from file:

import json

with open('data.txt', 'w') as f:

json.dump(dict1, f)

with open('data.txt', 'r') as f:

dict1=json.load(f)

json.dumps, json.loads 用于直接操作 json 格式数据 在python中，使其 human可读：

>>> print(json.dumps(data, sort_keys=True, indent=2))

{

"item": "Beer",

"cost": "£4.00"

}

>>> json.loads('["foo", {"bar":["baz", null, 1.0, 2]}]')

['foo', {'bar': ['baz', None, 1.0, 2]}]

人类可读 in SHELL#

cat ./output/pre_file_name.json | python -m json.tool

#Handle list of items in file

list_UC.txt

edn1-uc-cup01

edn1-uc-cucm02

esg3-uc-cuc01

playbook.yml

with open("./list_UC") as file: # Use file to refer to the file object

Targets = file.readlines()

print (Targets)

for host in Targets:

print (host.strip())

注意！ w/a 模式无法读取文件内容。

>>> print (f.read())

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

IOError: File not open for reading

必须改为 “r” 模式打开

>>> f1=open("newtext.txt","r")

>>> print (f1.readlines())

['Hello world!']

输出一遍后指针会停留在末尾，利用seek(0) 吧指针调回起始点， 或者使用with 语句.

>>> f1=open("newtext.txt","w")

>>> f1.write("Hello World!")

>>> f1=open("newtext.txt","a")

>>> f1.write("\n")

>>> f1.write("This is AirBnB Dublin")

>>> f1=open("newtext.txt","r")

>>> print (f1.read())

Hello World!

This is AirBnB Dublin

>>>print (f1.read())

>>> f1.seek(0)

>>> print (f1.read())

Hello World!

This is AirBnB Dublin

======================================================

>>> with open("newtext.txt") as f2:

... print (f2.read())

...

Hello World!

This is AirBnB Dublin