Python编程中的文件读写及相关的文件对象方法讲解
python文件读写
python 进行文件读写的内建函数是open或file
file_hander(文件句柄或者叫做对象)= open(filename,mode)
mode：
模式 说明
r 只读
r+ 读写
w 写入,先删除源文件,在重新写入,如果文件没有则创建
w+ 读写,先删除源文件,在重新写入,如果文件没有则创建(可以写入写出)
读文件:
>>> fo = open("/root/a.txt")
>>> fo
<open file '/root/a.txt', mode 'r' at 0x7f5095dec4e0>
>>> fo.read()
'hello davehe\ni am emily\nemily emily\n'
>>> fo.close() >>> fo.read() #对象已关闭，在读取就读不到
Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: I/O operation on closed file
>>> f1 = file("/root/a.txt")
>>> f1.read()
'hello davehe\ni am emily\nemily emily\n'
>>> f1.close()
写文件:
root@10.1.6.200:~# ls -l new.txt
ls: cannot access new.txt: No such file or directory
>>> fnew = open("/root/new.txt",'w') w参数文件没有则创建
>>> fnew.write('hello \n i am dave')
这时查看文件数据其实还只是在缓存区中,没有真正落到文件上.
root@10.1.6.200:~# cat new.txt root@10.1.6.200:~#
只要我把文件关闭,数据会从缓存区写到文件里
>>> fnew.close() root@10.1.6.200:~# cat new.txt
hello i am dave
再次使用w参数,文件会被清空,所以用该参数需要谨慎.
>>> fnew = open("/root/new.txt","w")
root@10.1.6.200:~# cat new.txt root@10.1.6.200:~#
mode使用r+参数:
>>> fnew = open("/root/new.txt",'r+')
>>> fnew.read()
'hello dave'
>>> fnew.write('i am dave')
>>> fnew.close()
root@10.1.6.200:~# cat new.txt
hello davei am dave
这次打开文件,直接写入,会发现ooo替换开头字母,因为上面读取操作使用了指针在写就写在后面.而这次是直接从头写入.
>>> fnew = open("/root/new.txt",'r+')
>>> fnew.write('ooo')
>>> fnew.close()
root@10.1.6.200:~# cat new.txt
ooolo davei am dave
文件对象方法
下面文件对象方法
- FileObject.close()
- String=FileObject.readline([size])
- List = FileObject.readlines([size])
- String = FileObject.read([size]) read:读取所有数据
- FileObject.next()
- FileObject.write(string)
- FileObject.writelines(List)
- FlieObject.seek(偏移量,选项)
- FlieObject.flush() 提交更新
>>> for i in open("/root/a.txt"): 用open可以返回迭代类型的变量,可以逐行读取数据
... print i
...
hello davehe i am emily emily emily
FileObject.readline: 每次读取文件的一行,size是指每行每次读取size个字节，直到行的末尾，超出范围会读取空字符串
>>> f1 = open("/root/a.txt")
>>> f1.readline()
'hello davehe\n'
>>> f1.readline()
'i am emily\n'
>>> f1.readline()
'emily emily\n'
>>> f1.readline() '' >>> f1.readline() '' >>>f1.close()
FileObject.readlines:返回一个列表
>>> f1 = open("/root/a.txt")
>>> f1.readlines()
['hello davehe\n', 'i am emily\n', 'emily emily\n']''
FileObject.next:返回当前行,并将文件指针到下一行,超出范围会给予警示,停止迭代.
>>> f1 = open("/root/a.txt")
>>> f1.next()
'hello davehe\n'
>>> f1.next()
'i am emily\n'
>>> f1.next()
'emily emily\n'
>>> f1.next()
Traceback (most recent call last): File "<stdin>", line 1, in <module> StopIteration
FileObject.write:write和后面writelines在写入前会是否清除文件中原来所有的数据,在重新写入新的内容,取决于打开文件的模式.
FileObject.writelines(List):多行写,效率比write高,速度更快,少量写入可以使用write
>>> l = ["python\n","python\n","python\n"]
>>> f1 = open('/root/a.txt','a')
>>> f1.writelines(l)
>>> f1.close()
root@10.1.6.200:~# cat a.txt
hello davehe i am emily emily emily python python python
FlieObject.seek(偏移量,选项):可以在文件中移动文件指针到不同的位置.
位置的默认值为0,代表从文件开头算起(即绝对偏移量),1代表从当前位置算起,2代表从文件末尾算起.
>>> f1 = open('/root/a.txt','r+')
>>> f1.read()
'hello davehe\ni am emily\nemily emily\npython\npython\npython\n'
>>> f1.seek(0,0) 指针指到开头,在读 >>> f1.read()
'hello davehe\ni am emily\nemily emily\npython\npython\npython\n'
>>> f1.read() '' >>> f1.seek(0,0) >>> f1.seek(0,2) 指针指到末尾,在读 >>> f1.read() ''
下面看个小实例,查找a.txt中emily出现几次
root@10.1.6.200:~# vim file.py
#!/usr/bin/env python
import re
f1 = open('/root/a.txt')
count = 0
for s in f1.readlines():
li = re.findall("emily",s)
if len(li) > 0:
count = count + len(li)
print "this is have %d emily" % count
f1.close()
root@10.1.6.200:~# cat a.txt
hello davehe i am emily emily emily
root@10.1.6.200:~# python file.py
this is have 3 emily
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
AI Hentai Generator
Generate AI Hentai for free.
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Google AI announces Gemini 1.5 Pro and Gemma 2 for developers
Jul 01, 2024 am 07:22 AM
Google AI has started to provide developers with access to extended context windows and cost-saving features, starting with the Gemini 1.5 Pro large language model (LLM). Previously available through a waitlist, the full 2 million token context windo
How to download deepseek Xiaomi
Feb 19, 2025 pm 05:27 PM
How to download DeepSeek Xiaomi? Search for "DeepSeek" in the Xiaomi App Store. If it is not found, continue to step 2. Identify your needs (search files, data analysis), and find the corresponding tools (such as file managers, data analysis software) that include DeepSeek functions.
How do you ask him deepseek
Feb 19, 2025 pm 04:42 PM
The key to using DeepSeek effectively is to ask questions clearly: express the questions directly and specifically. Provide specific details and background information. For complex inquiries, multiple angles and refute opinions are included. Focus on specific aspects, such as performance bottlenecks in code. Keep a critical thinking about the answers you get and make judgments based on your expertise.
How to search deepseek
Feb 19, 2025 pm 05:18 PM
Just use the search function that comes with DeepSeek. Its powerful semantic analysis algorithm can accurately understand the search intention and provide relevant information. However, for searches that are unpopular, latest information or problems that need to be considered, it is necessary to adjust keywords or use more specific descriptions, combine them with other real-time information sources, and understand that DeepSeek is just a tool that requires active, clear and refined search strategies.
How to program deepseek
Feb 19, 2025 pm 05:36 PM
DeepSeek is not a programming language, but a deep search concept. Implementing DeepSeek requires selection based on existing languages. For different application scenarios, it is necessary to choose the appropriate language and algorithms, and combine machine learning technology. Code quality, maintainability, and testing are crucial. Only by choosing the right programming language, algorithms and tools according to your needs and writing high-quality code can DeepSeek be successfully implemented.
How to use deepseek to settle accounts
Feb 19, 2025 pm 04:36 PM
Question: Is DeepSeek available for accounting? Answer: No, it is a data mining and analysis tool that can be used to analyze financial data, but it does not have the accounting record and report generation functions of accounting software. Using DeepSeek to analyze financial data requires writing code to process data with knowledge of data structures, algorithms, and DeepSeek APIs to consider potential problems (e.g. programming knowledge, learning curves, data quality)
The Key to Coding: Unlocking the Power of Python for Beginners
Oct 11, 2024 pm 12:17 PM
Python is an ideal programming introduction language for beginners through its ease of learning and powerful features. Its basics include: Variables: used to store data (numbers, strings, lists, etc.). Data type: Defines the type of data in the variable (integer, floating point, etc.). Operators: used for mathematical operations and comparisons. Control flow: Control the flow of code execution (conditional statements, loops).
Problem-Solving with Python: Unlock Powerful Solutions as a Beginner Coder
Oct 11, 2024 pm 08:58 PM
Pythonempowersbeginnersinproblem-solving.Itsuser-friendlysyntax,extensivelibrary,andfeaturessuchasvariables,conditionalstatements,andloopsenableefficientcodedevelopment.Frommanagingdatatocontrollingprogramflowandperformingrepetitivetasks,Pythonprovid
