>>> 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()

讀取數(shù)據(jù)是后期數(shù)據(jù)處理的必要步驟。.txt是廣泛使用的數(shù)據(jù)文件格式。一些.csv, .xlsx等文件可以轉(zhuǎn)換為.txt 文件進行讀取。我常使用的是Python自帶的I/O接口，將數(shù)據(jù)讀取進來存放在list中，然后再用numpy科學計算包將list的數(shù)據(jù)轉(zhuǎn)換為array格式，從而可以像MATLAB一樣進行科學計算。

下面是一段常用的讀取txt文件代碼，可以用在大多數(shù)的txt文件讀取中

filename = 'array_reflection_2D_TM_vertical_normE_center.txt' # txt文件和當前腳本在同一目錄下，所以不用寫具體路徑
pos = []
Efield = []
with open(filename, 'r') as file_to_read:
  while True:
    lines = file_to_read.readline() # 整行讀取數(shù)據(jù)
    if not lines:
      break
      pass
     p_tmp, E_tmp = [float(i) for i in lines.split()] # 將整行數(shù)據(jù)分割處理，如果分割符是空格，括號里就不用傳入?yún)?shù)，如果是逗號， 則傳入‘，'字符。
     pos.append(p_tmp)  # 添加新讀取的數(shù)據(jù)
     Efield.append(E_tmp)
     pass
   pos = np.array(pos) # 將數(shù)據(jù)從list類型轉(zhuǎn)換為array類型。
   Efield = np.array(Efield)
   pass

例如下面是將要讀入的txt文件

經(jīng)過讀取后，在Enthought Canopy的variable window查看讀入的數(shù)據(jù)， 左側(cè)為pos，右側(cè)為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()   將文件內(nèi)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():                # 逐行讀取數(shù)據(jù)
line = line.strip()                #去掉每行頭尾空白
if not len(line) or line.startswith('#'):   # 判斷是否是空行或注釋行
continue                  #是的話，跳過不處理
result.append(line)              #保存
result.sort()                       #排序結(jié)果
print result
open('cdays-4-result.txt','w').write('%s' % '\n'.join(result))        #保存入結(jié)果文件