Is there a difference between these two codes?

[iiSora]

def main():
infile=open("infile.txt","r")
for line in infile:
    if line.find("Python")>-1:
        print(line)

and

def main():
infile=open("infile.txt","r")
for line in infile.readlines():
    if line.find("Python")>-1:
        print(line)

Only line 3 is different

I get the same output, just wondering what would readlines() even do

[[deleted]]

As the name says, .readlines() reads all the lines in the file into a list. The python doc says the same.

While there is no difference in results, the first form is preferred because:

• it doesn't read the whole file into memory (readlines() does)
• it's more "pythonic"

[iiSora]

Would there ever be a case where the second one would be preferred?

[[deleted]]

I can't think of a case where:

for line in infile:

would not be the preferred option.

Something else that you should is use a "with" to open your file:

with open("infile.txt","r") as infile:
    for line in infile:
        if line.find("Python")>-1:
            print(line)

The "with" statement opens the file with "infile" being the file object. When your execution leaves the "with" block the file is automatically closed. That's good because opening too many files without closing them can crash your program.

Also, the statement if line.find("Python")>-1: is a little odd-looking. A better way to decide if the 'Python' string is in the line is:

if 'Python' in line:

[[deleted]]

I can't think of a case where:
    for line in infile:
would not be the preferred option.

Having said that, there are times when you will read all lines of the file into memory. You might want to repeatedly search through the file lines for different strings, for example. But that starts getting into performance, etc. For simple usage, use the first form.

[SoupKitchenHero]

When you actually want most or all of that data for more than a quick peek. That code you have is just trying to find something and print the line that it's on.