Question

我是这个论坛的新手。编程＆amp;蟒蛇。我正在努力开发我的第一个程序，但是我不断遇到关于一个特定问题的问题。我很高兴，某种鞋底可以让我摆脱痛苦。告诉我如何正确地做我想做的事。如果你知道自己在做什么，我很确定这很简单，但此刻我很愚蠢。我不知道我在做什么： - ）

示例：

我需要使用2个文件，A＆amp;乙

文件A包含文字：

This is a test

文件B包含文字：

h
t
s
i
a

我需要创建一个程序，它将从文件A中一次抓取1个字符，然后搜索文件B以查找相同的字符。一旦程序找到匹配项，我希望它打印出找到匹配项的行号，然后继续从文件A＆amp;中抓取另一个字符。重复此过程直到EOF。

Answer 1

好的，让我们一步一步。首先，我会将文件B读入一个非常适合快速查找的结构，因为我们将经常这样做：

chars = {}
with open("B") as lookupfile:
    for number,line in enumerate(lookupfile):
        chars[line.strip()] = number

现在我们有一个字典chars，其中包含字母作为键，行号包含值：

>>> chars
{'t': 1, 'a': 4, 'i': 3, 'h': 0, 's': 2}

现在我们可以迭代第一个文件。文件的标准Python迭代器每次迭代消耗一个行，而不是一个字符，所以最好简单地将整个文件读入一个字符串然后迭代它（因为对于字符串，迭代是逐个字符的）：

with open("A") as textfile:
    text = textfile.read()

现在我们遍历字符串并打印匹配值：

for char in text:
    if char in chars:
        print("Character {0} found in row {1}".format(char, chars[char]))

如果您不喜欢两次访问字典，也可以使用

for char in text:
    found = chars.get(char):    # returns None if char isn't a key in chars
    if found:
        print("Character {0} found in row {1}".format(char, found))

或使用例外：

for char in text:
    try:
        print("Character {0} found in row {1}".format(char, chars[char]))
    except KeyError:
        pass

Answer 2

首先阅读文件A并将其内容存储在变量中（使用file.read）。

with open('A.txt') as f:

    data = f.read()  # now data is: "This is a test"
    # now data is string that dontains all data of the file A.
    # But as searching a character in a string is an O(N) operation
    # so we must convert this string to a better data-structure.
    # As we need the item as well as their first index so we
    # should create a dict here, with character as the key and
    # it's first appearance(first index) as it's value. 
    # Dicts provide O(1) lookup.

    dic = {}
    for ind, char in enumerate(data):
        # store the character in dict only if it is an alphabet
        # also check if it's already present is dict or not.
        if char.isalpha() and char not in dic:
            dic[char] = ind
    #dic is {'a': 8, 'e': 11, 'i': 2, 'h': 1, 's': 3, 'T': 0, 't': 10}

现在打开文件B并使用for循环迭代它，文件迭代器上的for循环一次返回一行。（内存有效方法）。

with open('B.txt') as f:
    for char in f:            #iterate one line at a time 
        char = char.strip()   #str.strip strips off whitespaces like '\n'
        if char in dic:
           print dic[char]     # if character is found in dict then
                              # print it's value, i.e index
...             
1
10
3
2
8

Answer 3

import os
fA = open('C:\\Desktop\\fileA.txt', 'r')
fB = open('C:\\Desktop\\fileB.txt', 'r')

fileb_content = []
for line in fB:
    fileb_content.append(fB.read().split('\n'))

rA = fA.readline().split('\n')[0]

for c in list(rA):
        if(c.strip()):
            if(c.lower() in fileb_content[0]):
                print(fileb_content[0].index(c.lower()))

在这里我测试该角色不是空的。

循环中的Python字符串比较

3 个答案: