打印找到的行数

Question

New to programming here and was wondering if anyone could help me out:

I'm trying to print or return the number of lines found in the below code using one line and I can't figure it out.

query = raw_input("Enter string to search for: ")
for line in open("list2.csv"):
    if query in line:
        print line,

Answer 1

Use a list comprehension like this:

with open("list2.csv") as f:
 print(sum(query in line for line in f))  #gives number of lines found 

Answer 2

There have been identical questions asked on here:

How to get line count cheaply in Python?

Here is the method that thread provides:

def file_len(fname):
with open(fname) as f:
    for i, l in enumerate(f):
        pass
return i + 1

Search is your friend :).

Answer 3

I would suggest for clarity that you avoid using just a single line! Here is something that should work:

query = raw_input("Enter string to search for: ")
lines = []
for line in open("list2.csv"):
    if query in line:
        lines.append(line)
        print line,
print "Number of lines:", len(lines)

If you really wanted a single line, you could do the following:

query = raw_input("Enter string to search for: ")
print "Number of lines:", len([line for line in open("list2.csv") if query in line])

Answer 4

Not sure if this would be the best option, but it's the easiest.

Add a counter to your if statement to increase by one for every time the if statement executes.

Try this:

counter = 0
query = raw_input("Enter string to search for: ")
for line in open("list2.csv"):
    if query in line:
        print line
        counter += 1
return counter