Python：查找和打印字符串，每行多个实例

Question

我找不到我的确切问题的答案，也无法与之相关。 这是我所拥有的：

file = input('put file name here: ')

try:
        fhand = open(file)

        for line in fhand:
                line = line.rstrip()
                if line.find('[') == -1: continue
                atpos1 = line.find('[')
                atpos2 = line.find(']')
                info = line[atpos1+1:atpos2]

                print(info)
except:
        print('incorrect file name')

print('you are done')
quit()

这对于括号之间的字符串的第一个实例非常有效，但有时每行有多个实例。如何打印文档中括号内的每一个单词/字符串？

Answer 1

你可以继续寻找括号，直到没有括号是这样的：

for line in fhand:
    line = line.rstrip()
    while line.find('[') != -1:
        atpos1 = line.find('[')
        atpos2 = line.find(']')
        info = line[atpos1+1:atpos2]
        line = line[atpos2:len(line)]
        print(info)

Answer 2

您使用 str.find(sub[, start[, end]]) 并在最后一次找到 ']' 之后使用 start 值进行新搜索 - 将其放入 while 循环，直到找不到更多 '['：

file = "t.txt"

with open(file,"w") as f:
    f.write("""nothing
some [one] some
some [one] some [two] more [three] things
some [one] some""")


try:
    with open(file) as f:
        for idx, line in enumerate(f,1):
            line = line.rstrip()
            pos = line.find('[')           # store first position
            while pos != -1:               # only continue if found
                atpos2 = line.find(']', pos)   # find end after pos
                info = line[pos+1:atpos2]      # get part

                pos = line.find('[',atpos2)    # find next start after end
                print(f"Found '{info}' in line {idx}") 
except Exception as e:  # maybe print the error as well...
        print('stop being a stupid', e)


print('you are done')

输出：

Found 'one' in line 2
Found 'one' in line 3
Found 'two' in line 3
Found 'three' in line 3
Found 'one' in line 4
you are done

atpos2 = line.find(']', pos) # find end after pos 部分对于像这样的字符串很重要

'this ] will give you [weird] outputs [ elsewise'