二维数组结构python

Question

I am taking a python class and have no experience in python. The instructor only teaches documentation and refuses to give code examples. I understand C++ but I'm getting very frustrated with python because I am basically teaching myself.

I want to open a text file that contains one string of random characters per line. The length could be 8, 10, 15, or 20 chars, for example. It has to be flexible. There can be an unspecified number of strings (lines) in the text file.

The text file might look like this for example:

HGAMONIHRA
AOMOKAWONS
NFROLBOBDN
ARFSIHCAGE
LNIEEWONOK
GOLFUNDTHC
KOCATAOHBI
AMRERCGANH
SLGFAMALLC
ALLIGATORX

I just want to figure out how to put each char in an array-like structure where I can access it like a 2d-array --> my array[2][3], for example.

I was practicing with a dictionary just to test the behavior. I thought that I could use a dictionary with a nested for loop and then use a tuple as a key and pass a parsed char from the string as a value. I was thinking this might work but when I try to make a dictionary work with just a single line, my print statement only gives me one key and one value and not the list. I am really confused. I know this is a pain but will someone please teach me in simple terms? python is leaving a nasty taste in my mouth.

This was my test code for just one line of a text file:

count = 0
text = open("puzzle.txt")
line = text.readline()
for i in line:  #this is probably the problem
    mydict = dict()
    mydict.update({count:line[count-1]}) #was hoping to make many keys and values.
    count += 1

print mydict.values() #want to see there are multiple dict values, each as a char.
print count #just checking to see what count value was

Can someone teach me because my instructor will not and I really want to learn.

Answer 1

Python strings are treated as immutable sets (alike a tuple), so you only need to hold a set of strings of each line.

count = 0
text = open("puzzle.txt", 'r')
myLines = text.readlines()

#Usage;
print myLines[0][0]
# Prints the first character

Because python strings are immutable you will need to set the whole index as a new string

myLines[0] = mylines[0:1] + 'G' + myLines[2:]

Answer 2

Your code has one obvious problem at first glance - you're resetting mydict to an empty dict each time through the loop, with your line:

    mydict = dict()

If you moved that so it was immediately before the loop, you could then test further to see whether there were other problems to fix.

However, there's a much more straightforward way to achieve what you want:

>>> with open("puzzle.txt") as f:
...     puzzle = [list(line.strip()) for line in f]

This opens your file puzzle.txt and assigns it to the variable f , then reads each line in the file into a string variable line , strips off any whitespace (including the newline at the end), converts the resulting string into a list of characters, and finally collects each of those lists into another list which it assigns to the variable puzzle . Finally, because all of this was done inside a with statement, the file is automatically closed.

There are a couple of important Python concepts in the code above:

• using the with statement, and iterating over the lines of a file
• list comprehensions

The result of this code can be seen more clearly if you use the pprint function in the pprint module:

>>> from pprint import pprint
>>> pprint(puzzle)
[['H', 'G', 'A', 'M', 'O', 'N', 'I', 'H', 'R', 'A'],
 ['A', 'O', 'M', 'O', 'K', 'A', 'W', 'O', 'N', 'S'],
 ['N', 'F', 'R', 'O', 'L', 'B', 'O', 'B', 'D', 'N'],
 ['A', 'R', 'F', 'S', 'I', 'H', 'C', 'A', 'G', 'E'],
 ['L', 'N', 'I', 'E', 'E', 'W', 'O', 'N', 'O', 'K'],
 ['G', 'O', 'L', 'F', 'U', 'N', 'D', 'T', 'H', 'C'],
 ['K', 'O', 'C', 'A', 'T', 'A', 'O', 'H', 'B', 'I'],
 ['A', 'M', 'R', 'E', 'R', 'C', 'G', 'A', 'N', 'H'],
 ['S', 'L', 'G', 'F', 'A', 'M', 'A', 'L', 'L', 'C'],
 ['A', 'L', 'L', 'I', 'G', 'A', 'T', 'O', 'R', 'X']]

... and you can access an individual character exactly as you proposed in your question:

>>> puzzle[2][3]
'O'

Answer 3

You could do it with a list of lists:

>>> with open('puzzle.txt') as f:
...   a = [list(line.rstrip()) for line in f]
... 
>>> a[0,3]
>>> a[0][3]
'M'
>>> a[1][0]
'A'