1、文件的打开和建立node
>>> f = open('/tmp/test.txt') >>> f.read() 'hello python!\nhello world!\n' >>> f <open file '/tmp/test.txt', mode 'r' at 0x7fb2255efc00>
2、文件的读取python
步骤:打开 -- 读取 -- 关闭正则表达式
>>> f = open('/tmp/test.txt') >>> f.read() 'hello python!\nhello world!\n' >>> f.close()
3、文件写入(慎重,当心别清空本来的文件)缓存
直接的写入数据是不行的,由于默认打开的是'r' 只读模式app
>>> f.write('hello boy') Traceback (most recent call last): File "<stdin>", line 1, in <module> IOError: File not open for writing >>> f <open file '/tmp/test.txt', mode 'r' at 0x7fe550a49d20>
应该先指定可写的模式ide
>>> f1 = open('/tmp/test.txt','w') >>> f1.write('hello boy!')
但此时数据只写到了缓存中,并未保存到文件,并且从下面的输出能够看到,原先里面的配置被清空了ui
[root@node1 ~]# cat /tmp/test.txt [root@node1 ~]#
关闭这个文件便可将缓存中的数据写入到文件中spa
>>> f1.close() [root@node1 ~]# cat /tmp/test.txt [root@node1 ~]# hello boy!
>>> f2 = open('/tmp/test.txt','r+') >>> f2.write('\nhello aa!') >>> f2.close() [root@node1 python]# cat /tmp/test.txt hello aay!
如何实现不替换?指针
>>> f2 = open('/tmp/test.txt','r+') >>> f2.read() 'hello girl!' >>> f2.write('\nhello boy!') >>> f2.close() [root@node1 python]# cat /tmp/test.txt hello girl! hello boy!
能够看到,若是在写以前先读取一下文件,再进行写入,则写入的数据会添加到文件末尾而不会替换掉原先的文件。这是由于指针引发的,r+ 模式的指针默认是在文件的开头,若是直接写入,则会覆盖源文件,经过read() 读取文件后,指针会移到文件的末尾,再写入数据就不会有问题了。这里也能够使用a 模式orm
>>> f = open('/tmp/test.txt','a') >>> f.write('\nhello man!') >>> f.close() >>> [root@node1 python]# cat /tmp/test.txt hello girl! hello boy! hello man!
关于其余模式的介绍,见下表:
模式 |
描述 |
r |
以读方式打开文件,可读取文件信息。 |
w |
以写方式打开文件,可向文件写入信息。如文件存在,则清空该文件,再写入新内容 |
a |
以追加模式打开文件(即一打开文件,文件指针自动移到文件末尾),若是文件不存在则建立 |
r+ |
以读写方式打开文件,可对文件进行读和写操做。 |
w+ |
消除文件内容,而后以读写方式打开文件。 |
a+ |
以读写方式打开文件,并把文件指针移到文件尾。 |
b |
以二进制模式打开文件,而不是以文本模式。该模式只对Windows或Dos有效,类Unix的文件是用二进制模式进行操做的。 |
>>> f = open('/tmp/test.txt') >>> f.readline() 'hello girl!\n' >>> f.readline() 'hello boy!\n' >>> f.readline() 'hello man!' >>> f.readline() ''
方法二:
>>> for i in open('/tmp/test.txt'): ... print i ... hello girl! hello boy! hello man!
f.readlines() 将文件内容以列表的形式存放
>>> f = open('/tmp/test.txt') >>> f.readlines() ['hello girl!\n', 'hello boy!\n', 'hello man!'] >>> f.close()
f.next() 逐行读取数据,和f.readline() 类似,惟一不一样的是,f.readline() 读取到最后若是没有数据会返回空,而f.next() 没读取到数据则会报错
>>> f = open('/tmp/test.txt') >>> f.readlines() ['hello girl!\n', 'hello boy!\n', 'hello man!'] >>> f.close() >>> >>> f = open('/tmp/test.txt') >>> f.next() 'hello girl!\n' >>> f.next() 'hello boy!\n' >>> f.next() 'hello man!' >>> f.next() Traceback (most recent call last): File "<stdin>", line 1, in <module> StopIteration
f.writelines() 多行写入
>>> l = ['\nhello dear!','\nhello son!','\nhello baby!\n'] >>> f = open('/tmp/test.txt','a') >>> f.writelines(l) >>> f.close() [root@node1 python]# cat /tmp/test.txt hello girl! hello boy! hello man! hello dear! hello son! hello baby!
f.seek(偏移量,选项)
>>> f = open('/tmp/test.txt','r+') >>> f.readline() 'hello girl!\n' >>> f.readline() 'hello boy!\n' >>> f.readline() 'hello man!\n' >>> f.readline() ' ' >>> f.close() >>> f = open('/tmp/test.txt','r+') >>> f.read() 'hello girl!\nhello boy!\nhello man!\n' >>> f.readline() '' >>> f.close()
选项=0,表示将文件指针指向从文件头部到“偏移量”字节处
选项=1,表示将文件指针指向从文件的当前位置,向后移动“偏移量”字节
选项=2,表示将文件指针指向从文件的尾部,向前移动“偏移量”字节
>>> f = open('/tmp/test.txt','r+') >>> f.seek(0,2) >>> f.readline() '' >>> f.seek(0,0) >>> f.readline() 'hello girl!\n' >>> f.readline() 'hello boy!\n' >>> f.readline() 'hello man!\n' >>> f.readline() ''
f.flush() 将修改写入到文件中(无需关闭文件)
>>> f.write('hello python!') >>> f.flush() [root@node1 python]# cat /tmp/test.txt hello girl! hello boy! hello man! hello python!
f.tell() 获取指针位置
>>> f = open('/tmp/test.txt') >>> f.readline() 'hello girl!\n' >>> f.tell() 12 >>> f.readline() 'hello boy!\n' >>> f.tell() 23
4、内容查找和替换
1、内容查找
实例:统计文件中hello个数
思路:打开文件,遍历文件内容,经过正则表达式匹配关键字,统计匹配个数。
[root@node1 ~]# cat /tmp/test.txt hello girl! hello boy! hello man! hello python!
#!/usr/bin/python import re f = open('/tmp/test.txt') source = f.read() f.close() r = r'hello' s = len(re.findall(r,source)) print s [root@node1 python]# python count.py 4
方法二:
#!/usr/bin/python import re fp = file("/tmp/test.txt",'r') count = 0 for s in fp.readlines(): li = re.findall("hello",s) if len(li)>0: count = count + len(li) print "Search",count, "hello" fp.close() [root@node1 python]# python count1.py Search 4 hello
#!/usr/bin/python import re f1 = open('/tmp/test.txt') f2 = open('/tmp/myhello.txt','r+') for s in f1.readlines(): f2.write(s.replace('hello','hi')) f1.close() f2.close() [root@node1 python]# touch /tmp/myhello.txt [root@node1 ~]# cat /tmp/myhello.txt hi girl! hi boy! hi man! hi python!
实例:读取文件test.txt内容,去除空行和注释行后,以行为单位进行排序,并将结果输出为result.txt。test.txt 的内容以下所示:
#some words Sometimes in life, You find a special friend; Someone who changes your life just by being part of it. Someone who makes you laugh until you can't stop; Someone who makes you believe that there really is good in the world. Someone who convinces you that there really is an unlocked door just waiting for you to open it. This is Forever Friendship. when you're down, and the world seems dark and empty, Your forever friend lifts you up in spirits and makes that dark and empty world suddenly seem bright and full. Your forever friend gets you through the hard times,the sad times,and the confused times. If you turn and walk away, Your forever friend follows, If you lose you way, Your forever friend guides you and cheers you on. Your forever friend holds your hand and tells you that everything is going to be okay.
脚本以下:
f = open('cdays-4-test.txt') result = list() for line in f.readlines(): # 逐行读取数据 line = line.strip() #去掉每行头尾空白 if not len(line) or line.startswith('#'): # 判断是不是空行或注释行 continue #是的话,跳过不处理 result.append(line) #保存 result.sort() #排序结果 print result open('cdays-4-result.txt','w').write('%s' % '\n'.join(result)) #保存入结果文件