taking a character input in python from a file?
in python , suppose i have file data.txt . which has 6 lines of data . I want to calculate the no of lines which i am planning to do by going through each character and finding out the number of '\n' in the file . How to take one character input from the file 开发者_JAVA百科? Readline takes the whole line .
I think the method you're looking for is readlines
, as in
lines = open("inputfilex.txt", "r").readlines()
This will give you a list of each of the lines in the file. To find out how many lines, you can just do:
len(lines)
And then access it using indexes, like lines[3]
or lines[-1]
as you would any normal Python list.
You can use read(1)
to read a single byte. help(file)
says:
read(
size)
-> read at most size bytes, returned as a string.If the size argument is negative or omitted, read until EOF is reached. Notice that when in non-blocking mode, less data than what was requested may be returned, even if no size parameter was given.
Note that reading a file a byte at a time is quite un-"Pythonic". This is par for the course in C, but Python can do a lot more work with far less code. For example, you can read the entire file into an array in one line of code:
lines = f.readlines()
You could then access by line number with a simple lines[lineNumber]
lookup.
Or if you don't want to store the entire file in memory at once, you can iterate over it line-by-line:
for line in f:
# Do whatever you want.
That is much more readable and idiomatic.
It seems the simplest answer for you would be to do:
for line in file:
lines += 1
# do whatever else you need to do for each line
Or the equivalent construction explicitly using readline()
. I'm not sure why you want to look at every character when you said above that readline()
is correctly reading each line in its entirety.
To access a file based on its lines, make a list of its lines.
with open('myfile') as f:
lines = list(f)
then simply access lines[3]
to get the fourth line and so forth. (Note that this will not strip the newline characters.)
The linecache module can also be useful for this.
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