readline（）仅读取第一行

Question

I'm trying to read multiple lines in a file and it doesn't seem to work when I assigned my readline() method to a variable. It keeps printing the first line. It only seems to work when I don't assign it to a variable. Any ideas?

I'm using Python 3.6.2. Here is my code:

# This is it not working ( I omitted the 'gradesfile_path' variable)

gradesfile = open(gradesfile_path,'r')
readgrades = gradesfile.readline()

print(readgrades)
print(readgrades)

# This is working when I don't call the variable

print(gradesfile.readline())
print(gradesfile.readline())
print(gradesfile.readline())

Answer 1

readline() reads a single line -- the next line in the context of the iterator returned by open() . And you are assigning the line read as variable readgrades which will always contain that line.

Perhaps you meant to assign the method to a variable and call that variable instead:

readgrades = gradesfile.readline  ##Note the absence of call

Then you can do:

readgrades()

Answer 2

当您将gradesfile.readline()分配给变量时，实际上是在读取一行并将该行存储到变量中

Answer 3

readline() is suppose to read the whole file as line by line, so I believe you need to keep calling it everytime you need to read a line and If you're not restricted to use readline(), then your objective can be achieved using:

read() :- will read the whole file at once

readlines() :- will read the whole file and result it into python list

with open('file_name', 'r') as file_obj:
    print file_obj.readlines()

or

with open('file_name', 'r') as file_obj:
    some_var = file_obj.readlines()
    print some_var

or

with open('file_name', 'r') as file_obj:
    print file_obj.read()

or

with open('file_name', 'r') as file_obj:
    some_var = file_obj.read()
    print some_var