替换Python 3中的文本，但只能读取一行

Question

我正在尝试使用搜索并在Python 3中用文件替换

但是当我尝试我的代码时，它仅在第一行起作用，而不是遍历每一行并替换它。

到目前为止我正在尝试

f1 = open('test.txt', 'r')
f2 = open('test2.txt', 'w')
for line in f1:
    f1.readlines()
    find = (input('Enter word to find: '))
    while find in line:
        print('Word Found')
        replace = input('Enter Word to replace with: ')
        replace_action = (input('Are you sure you want to replace Y or N:'))
        if replace_action.lower() == 'y':
            f2.write(line.replace(find.lower(), replace))
        else:
            print('You have cancelled this operation')
    else:
        print('Word not found in file')
f1.close()
f2.close()

这段代码仅读取第一行，而不再起作用。

Answer 1

发生这种情况是因为您没有正确读取文件。

for line in f1:
    f1.readlines()

f1.readlines（）消耗所有文件行，并返回字符串列表。
您只需要删除f1.readlines（）行。

如果您想了解以python读取文件的各种方式，请查阅文档。 https://docs.python.org/2.7/tutorial/inputoutput.html
https://docs.python.org/3/tutorial/inputoutput.html

Answer 2

f1 = open('test.txt', 'r')
f2 = open('test2.txt', 'w')

lines = f1.readlines()

find = (input('Enter word to find: '))
replace = input('Enter Word to replace with: ')
for line in lines:
    print('current line: {}'.format(line))

    if not find in line:
        print('world {} not found in this line. Moving to next line'.format(find))
        continue

    print('World {} found in this line'.format(find))

    replace_action = input('Are you sure you want to replace for this line y or n')

    if replace_action.lower() == 'y':
        line = line.replace(find.lower(), replace)
        f2.write(line)
        print("New line: {}".format(line))
    else:
        print('You have cancelled this operation')

    print("")

f1.close()
f2.close()

Answer 3

该方法readlines()读取直到EOF使用readline()并返回包含行的列表。

f1 = open('test.txt', 'r')
f2 = open('test2.txt', 'w')

f1_lines = f1.readlines()
f1.close()

for line in f1_lines:
    find = input('Enter word to find: ')
    if find in line:
        print('Word Found')
        replace = input('Enter Word to replace with: ')
        replace_action = input('Are you sure you want to replace Y or N:')
        if replace_action.lower() == 'y':
            f2.write(line.replace(find.lower(), replace))
        else:
            print('You have cancelled this operation')
    else:
        print('Word not found in file')
        f2.write(line)

f2.close()

根据对问题的了解，我改变了一些想法。 if find in line检查您要查找的输入是否在行中。 如果是，则使用替换将行写入f2，否则将行直接写入f2。

编辑：我猜你还有另一个问题。 为我工作。

runfile('C:/Users/mathieu.scheltienne/Desktop/test/untitled0.py', wdir='C:/Users/mathieu.scheltienne/Desktop/test')

Enter word to find: hello
Word Found

Enter Word to replace with: good bye

Are you sure you want to replace Y or N:y

Enter word to find: hello
Word Found

Enter Word to replace with: good bye

Are you sure you want to replace Y or N:y

Enter word to find: hello
Word Found

Enter Word to replace with: good bye

Are you sure you want to replace Y or N:y

输入文件为：test.txt

hello world
hello galaxy
hello universe

输出文件：

good bye world
good bye galaxy
good bye universe

仅包含一个单词的版本，每行仅将替换为一个单词：

f1 = open('test.txt', 'r')
f2 = open('test2.txt', 'w')

f1_lines = f1.readlines()
f1.close()

find = input('Enter word to find: ')
replace = input('Enter Word to replace with: ')
counter = 0

for line in f1_lines:
    if find in line:
        print('Word Found')
        f2.write(line.replace(find.lower(), replace))
        counter += 1
    else:
        f2.write(line)

if counter == 0:
    print('Word not found in file')
else:
    print('{} words replaced'.format(counter))

f2.close()

Answer 4

我认为您已经有了解决方案，但是很少有地方可以优化它。

• 使用python contextmanager with处理文件，那么您不必担心关闭它。 在您的情况下，如果在for循环期间抛出异常，则不会关闭文件。
• with您一起使用不需要调用readline() 。
• 如果从外部来源获取输入，请使用try/catch块。

这是另一种方法。

def  readfile_and_replace(input_filename, output_filename):
     #using python context manager to open file. File will be closed even in case of exception
     with open(input_filename) as input_file:
        with open(output_filename,'w') as output_file:
            try:
                for line in input_file:
                    search_str = (input('Enter word to find: '))
                    new_line = line
                    if search_str in line:
                        replace_str = input('Enter Word to replace with: ')
                        if input('Are you sure you want to replace Y or N:').upper() == 'Y':
                            new_line = line.replace(search_str.lower(), replace_str)
                            #print(line.replace(search_str.lower(), replace_str))
                        else:
                            print('You have cancelled this operation')
                    else :
                        print('Word not found in current line')

                    output_file.write(new_line)
            except KeyboardInterrupt:
                print("user aborted the program")


readfile_and_replace(input_filename='logs.txt', output_filename='logs2.txt') 

希望对您有所帮助。