python文件列表搜索（我有两个匹配的字符串，但是python认为它们不相等）

Question

if your input is john why isn't the if statement kicking in????

studentname.txt

john 34
paul 37
poop 45

above is whats in studentname.txt

b=a
name = input('students name : ')
list1=[]

file=open('studentname.txt','r')
for (a) in file:
    list1.append(a)    
    b=a[:-3]    

why isn't this next if statement tripping if name entered is 'john' for instance??

    if name == b:
        print(a)

file.close

Answer 1

You are picking up newlines. Depending on the os you created the file on, you'll have different new line characters. The safest way to rid yourself of this is:

a = a.rstrip()

That will take care of any trailing whitespace.

You could also do:

for a in map(lambda x: x.rstrip(), file):

Also, don't name your variable 'file'. This is a python built-in function that you've now renamed for your script and any script that imports it.

Finally, you might prefer to handle files like this:

with open("studentname.txt", 'r') as testfile:
    for item in (line.rstrip() for line in testfile):
        print item

No need to close the file, the with statement controls it's scope and closes it.

Answer 2

或者，您可以使用a.strip()[:-3] ，它将在获取子字符串之前修剪所有空白字符。

Answer 3

Try this:

for a in file.readlines():
    name, _, score = a.strip().partition(' ')
    if name == b:
        print(a)

It is cleaner in that it doesn't rely on a 2-digit value and is more expressive than arbitrary indexes. It also strips carriage returns and newlines.

Answer 4

Your immediate problem is as others have mentioned that you are not aware of the \\n at the end of your data. print and the repr built-in function are your friends; use them:

if name != b:
    print repr(name), repr(b)

whereupon the cause of the problem becomes obvious.

Here is some (untested) code that illustrates better practice when handling simple data file formats like yours. It is intended to cope with blank/empty lines, unterminated last line, and real-life possibilities like:

Jack 9
Jill 100
Billy Bob 99
Decimus 1.23
Numberless

without crashing or running amok.

with open('studentname.txt','rU') as f:
    for line_number, line in enumerate(f, 1):
        line = line.rstrip('\n')
        fields = line.split()
        nf = len(fields]
        if nf == 0: 
            continue: # blank/empty line
        if nf == 1:
            print('Only 1 field in line', line_number, repr(line))
            continue
        dataname = ' '.join(fields[:-1])
        try:
            datanumber = int(fields[-1])
        except ValueError:
            print('Invalid number', repr(fields[-1]), 'in line',
                line_number, repr(line))
            continue
    list1.append((dataname, datanumber))   
    if name == dataname:
        print(repr(dataname), number)

Note file.close evaluates to a method/function object, which does nothing. You need to call it: file.close() . However now that you are using the with statement, it will look after closing the file, so just delete that file.close line.