Python读写txt文本文件的操作方法全解析

>>> f = open('/tmp/test.txt')
>>> f.read()
'hello python!\nhello world!\n'
>>> f
<open file '/tmp/test.txt', mode 'r' at 0x7fb2255efc00>

>>> f = open('/tmp/test.txt')
>>> f.read()
'hello python!\nhello world!\n'
>>> f.close()

读取数据是后期数据处理的必要步骤。.txt是广泛使用的数据文件格式。一些.csv, .xlsx等文件可以转换为.txt 文件进行读取。我常使用的是Python自带的I/O接口，将数据读取进来存放在list中，然后再用numpy科学计算包将list的数据转换为array格式，从而可以像MATLAB一样进行科学计算。

下面是一段常用的读取txt文件代码，可以用在大多数的txt文件读取中

filename = 'array_reflection_2D_TM_vertical_normE_center.txt' # txt文件和当前脚本在同一目录下，所以不用写具体路径
pos = []
Efield = []
with open(filename, 'r') as file_to_read:
  while True:
    lines = file_to_read.readline() # 整行读取数据
    if not lines:
      break
      pass
     p_tmp, E_tmp = [float(i) for i in lines.split()] # 将整行数据分割处理，如果分割符是空格，括号里就不用传入参数，如果是逗号， 则传入‘，'字符。
     pos.append(p_tmp)  # 添加新读取的数据
     Efield.append(E_tmp)
     pass
   pos = np.array(pos) # 将数据从list类型转换为array类型。
   Efield = np.array(Efield)
   pass

例如下面是将要读入的txt文件

经过读取后，在Enthought Canopy的variable window查看读入的数据， 左侧为pos，右侧为Efield。

>>> 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>

>>> f1 = open('/tmp/test.txt','w')
>>> f1.write('hello boy!')

[root@node1 ~]# cat /tmp/test.txt
[root@node1 ~]#

>>> 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!

>>> 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!

>>> 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!

>>> f = open('/tmp/test.txt')
>>> f.readline()
'hello girl!\n'
>>> f.readline()
'hello boy!\n'
>>> f.readline()
'hello man!'
>>> f.readline()
''

>>> 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 = 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

>>> 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 = 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()

>>> 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.write('hello python!')
>>> f.flush()

[root@node1 python]# cat /tmp/test.txt

hello girl!
hello boy!
hello man!
hello python!

>>> f = open('/tmp/test.txt')
>>> f.readline()
'hello girl!\n'
>>> f.tell()
12
>>> f.readline()
'hello boy!\n'
>>> f.tell()
23

[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

#!/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!

#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. 

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('#'):   # 判断是否是空行或注释行
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