Python：了解使用 enumerate with readline 时的索引

Question

Python code:

myfile = open("test-file.csv", "r")
for k, line in enumerate(myfile,0):
   if k == 0:
      myline = myfile.readline()
      print(myline)
      break
myfile.close()

and test-file.csv is:

0. Zeroth
1. First
2. Second
3. Third

The output is

1. First

Why don't I get

0. Zeroth

?

Answer 1

By the time you call myfile.readline() you have already consumed the zeroth line. (It is stored in the variable line , and the variable k holds its index 0, which is the condition you are checking).

Then, you read another line (the "first" line) from myfile . Try printing line instead of myline .

Answer 2

Because "zeroth" has already been read in the loop,

 myfile = open("test-file.csv", "r")
 for k, line in enumerate(myfile,0):
   if k == 0:
      print(line) # this should output "zeroth"
      myline = myfile.readline() #this will read "First"
      print(myline)
      break
myfile.close()