在列表中查找字符索引

Question

我想在 .txt 文件中搜索某个字符 (X)，如果存在，则执行某个操作。不幸的是这段代码不起作用：

file = "test.txt"

file = open(file, "r") 

lines = file.readlines()

# char in the list

if "X" in lines:

    print('X is present in the list')

# char not in the list

if "X" not in lines:

    print('X is not present in the list')

测试.txt 文件：

XX X XXX X XX

XXXXX XX X    XX

有什么想法吗？

PS：即使将“X”更改为“X”也不起作用。

Answer 1

如果您需要知道X出现的行号：target = 'X'counter = 0with open('testing.txt') as f:    for i, line in enumerate(f):        if target in line:            counter += 1            print('target is present in line {}'.format(                i+1))print('target appears in {} lines'.format(counter))如果您还需要知道X出现的列号：target = 'X'counter = 0with open('testing.txt') as f:    for i, line in enumerate(f):        for j, char in enumerate(line):            if target == char:                counter += 1                print('target is present in line {} at column {}'.format(                    i+1, j+1))print('target appears {} times'.format(counter))一些澄清：with ... open完成后自动关闭文件，因此您无需记住显式关闭它for i, line in enumerate(f):逐行迭代，而不将它们一次性全部加载到内存中。

Answer 2

由于readlines()是一个列表，您需要迭代并签入行。也许您可以用于for else此目的：file = "testing.txt"file = open(file, "r")&nbsp;lines = file.readlines()# char in the listfor line in lines:&nbsp; &nbsp; if "X" in line:&nbsp; &nbsp; &nbsp; &nbsp; print('X is present in the list')&nbsp; &nbsp; &nbsp; &nbsp; breakelse:&nbsp; &nbsp; print('X is not present in the list')它迭代每一行，如果任何行有字符，则break仅else在任何行中都找不到字符时才运行。更新如果你想计数，那么你可以简单地在循环中增加计数器，一旦循环完成检查计数器：file = "testing.txt"file = open(file, "r")&nbsp;lines = file.readlines()# char in the listcounter = 0for line in lines:&nbsp; &nbsp; if "X" in line:&nbsp; &nbsp; &nbsp; &nbsp; counter += 1&nbsp; # < -- count&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;if counter: # check&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; print('X is present in the list')&nbsp; &nbsp; &nbsp; &nbsp;&nbsp;else:&nbsp; &nbsp; print('X is not present in the list')&nbsp;

Answer 3

正如您所要求的，我将输出一个包含 item 的列表Yes, there are 3 X's。我有我的dataf.txt文件：XXX X XX X XXX ASD X F FFFF XXD X XXX X EFXA F G将数据读入文件并计算 X 的数量（注意：我使用了列表理解 hack！）with open('dataf.txt','r') as fl:&nbsp; &nbsp; data = fl.readlines()&nbsp; &nbsp; a = ['Yes, there are '+str(i.count('X')) + " X's" if 'X' in i else "No X's" for i in data]&nbsp; &nbsp; print(a)输出：["Yes, there are 9 X's", "Yes, there are 4 X's", "Yes, there are 6 X's", "No X's"]