Python applet, for file operations and other

The following is a few of their own written on the file operation of the small program, which involves file operations, lists (collections, dictionaries) and other applications. For example, reading a row of data from a file, storing it in a list, and then manipulating the list, such as removing duplicates, sorting, and so on.

Common actions for a row in a file:

#这里列出两个常用的方法

• Method : Reads all rows at once

>>> f = file (' 1.txt ') >>> while 1:lines = F.readlines () if not lines:breakfor line in Lines:print line

• Method: A row of rows reads

>>> f = file (' 1.txt ') >>> while f:line = F.readline () If Len [line] = = 0:breakelse:print line,

Common list deduplication operations:

• Method 01: Function Processing

#列表中值超过1者表示有重复则删除, such as:

#列表顺序 ==> Change

>>> List1.count (3)  #元素值为3的个数: 2 2>>> def removedup (LST): For x in Lst:if lst.count (x) >1:del LST [Lst.index (x)]>>> lst = [1,3,2,4,3]>>> removedup (LST) >>> lst[1, 2, 4, 3]

• Method 02: General Methods

#建新空列表, iterate through the original list, if it is not in the new empty list, add

#列表顺序 ==> unchanged

>>> List1 = [1,3,2,4,3]>>> List2 = []>>> for i in List1:if I not in list2:list2.append (i) >&G T;> list2[1, 3, 2, 4]

• Method 03: Dictionary Methods

#利用字典key值的唯一性, and the Fromkeys () and keys () method inside

>>> List1 = [1,3,2,4,3]>>> List2 = {}.fromkeys (list1). Keys () >>> list2[1, 2, 3, 4]

• Method 04: Collection method

#集合能去除列表中重复项

#列表顺序 ==> Change

>>> List1 = [1,3,2,4,3]>>> Set (list1) set ([1, 2, 3, 4])

• Method 05: Iteration Tools

#用itertools的迭代工具的groupby () method

#列表顺序 ==> Change

• Method 06: Index Sorting

#先用集合, then sort, note key=list1.index, control order

# List Order ==> change

>>> List1 = [1,3,2,4,3]>>> List2 = List (set (List1)) >>> List2.sort (Key=list1.index) >> > List2[1, 3, 2, 4]

Common for string inversion operations:

• Method 01: List slices

>>> s = ' Hello '    >>> l = List (s) >>> l[::-1][' o ', ' l ', ' l ', ' e ', ' H ']

• Method 02: General Practice

>>> def Rev (s): Str0 = ' l    = len (s) -1while l >=0:STR0 + s[l]l-  = 1return str0>>> s = ' A B C D ' >>> rev (s) ' D C B A '

• Method 03: List Inversion

>>> s = ' HELLO ' >>> l = list (s) >>> l.reverse ()  #列表reverse () method >>> '. Join (L)   #用空字符串join列表 ' Olleh '

• Method 04:reduce function

>>> def Rev (s): return reduce (lambda x,y:y+x, s) #匿名函数和reduce函数结合使用 >>> s = ' AB CD ' >>> rev (s) ' DC BA '

Applet One: Extract the same part of two files

F1 = open ("1.txt", "r+") F2 = Open ("2.txt", "r+") F3 = Open ("3.txt", "w+") All1 = F1.readlines ()    #先拿文件1中所有行取出all2 = F2.readlines ()    #再拿文件2中所有行取出f1. Close () F2.close () for L1 in All1: for    L2 in All2:        if L1.strip () ==l2.strip (): #比较行中内容是否一样            F3.write (L2)    else:        continueelse:    pass        print "#" *40f3.close ()

Applet Two: reverse read file

If the contents of the Test.txt file to be read are as follows:

Python
Perl
Java
Shell

file1 = File (' test.txt ', ' R ')   #打开文件句柄list1 = []                     #用一个空列表用于存放每行的内容while True: Line    = File1.readline ()    # Read    List1.append (Line.strip ()) #去除字符串空格    If Len (line) = = 0:         #如果没内容, interrupt break for                     L in List1[::-1] :          #反向遍历, then read out    print lfile1.close ()

Output Result:

Shell
Java
Perl
Python

Applet three: Operate on two text files

Requirements:

1. Removing duplicates from each file

2. Find the same item in two files

3. Working with two files in a collection

4. Manipulating the intersection of two files

#原始文件: Document 1, File 2f1 = file (' 1.txt ', ' r ') F2 = file (' 2.txt ', ' R ') #生成文件: Files 3, File 4, file 5, 6f3 = File (' same.txt ', ' w+ ') f4 = file (' Union.txt ', ' w+ ') f5 = file (' 1_diff.txt ', ' w+ ') f6 = file (' 2_diff.txt ', ' w+ ') #用空列表来存储原始文件的内容list1 = [] # Use an empty list to hold the contents of each row List2 = [] #用于存放文件2中的内容1_diff = [] #用于存放文件1中的去重部分2_diff = [] #用于存放文件2中的去重部分 # traverse two files while True:line1 = F1.readline () line2 = F2.readline () If Len (line1) ==0 or Len (line2) ==0:break else:list1.append ( line1) list2.append (line2) List1_uniq = set (list1) #排除第一个文件中重复的内容list2_uniq = set (list2) #注意应用集合排除重复的项目same = List1_uniq & List2_uniq #取交集union = List1_uniq | List2_uniq #取合集 # takes the intersection of two sets, writes to file 3 for I in Same:f3.write (i) #取两个集合的并集, writes to file 4 for I in Union:f4.write (i) #取列表1中部 The intersection of the list1_uniq:if with the common part for I in the Same:f5.write (i) #取列表2中部分, the intersection with the common part for I in List2_uniq:if N OT i in Same:f6.write (i) #关闭所有打开的文件句柄f1. Close () F2.close () F3.close () F4.close () F5.close () F6.close ()

Python applet, for file operations and other