Question

我使用random.randint生成一个随机数，然后将该数字赋给变量。然后我想打印带有我赋给变量的数字的行，但我不断收到错误：

列出索引超出范围

这是我尝试的内容：

f = open(filename. txt)
lines = f.readlines() 

rand_line = random. randint(1,10)
print lines[rand_line]

Answer 1

您想使用random.choice

import random
with open(filename) as f:
    lines = f.readlines()
    print(random.choice(lines))

Answer 2

这段代码是正确的，假设您打算将字符串传递给open函数，并且在点后面没有空格... 但是，要小心Python中的索引，即它从0开始而不是1，然后在len(your_list)-1结束。

使用random.choice会更好，但如果您想要遵循您的想法，那就更好了：

import random
with open('name.txt') as f:
    lines = f.readlines()
    random_int = random.randint(0,len(lines)-1)
    print lines[random_int]

由于randint包含两个边界，因此您必须查看len(lines)-1。

Answer 3

f = open(filename. txt)
lines = f.readlines() 

rand_line = random.randint(0, (len(lines) - 1))  # https://docs.python.org/2/library/random.html#random.randint
print lines[rand_line]

Answer 4

要获得随机行而不将整个文件加载到内存中，可以使用Reservoir sampling（样本大小为1）：

import System.Environment   
import System.Directory  
import System.IO 
import Data.List  

main :: IO ()
main = do 
      putStrLn "Insert a string"
      word <- getLine
      putStrLn "Insert a char"
      char <- getChar
      putStrLn "Insert a position"
      pos <- getLine *line which is skipped*
      let x = (read pos :: Int) *converts string into int*
      putStrLn "Adding char to list..."
      let newS = [(insertChar char word x)] *result of insertChar is set to 
      newS*
      putStrLn "Printed list: "
      print (newS) *print new string*
      putStrLn "Insert file name"
      file <- getLine
      putStrLn "Adding new string to file..."
      add file newS

insertChar :: a -> [a] -> Int -> [a]
insertChar x ys     1 = x:ys
insertChar x (y:ys) n = y:insertChar x ys (n-1)

add :: String -> [String] -> IO ()  
add fileName [item] = appendFile fileName item

此算法使用GHCI>main Insert a string hello world Insert a char s Insert a position Adding char to list... Printed list: ["*** Exception: Prelude.read: no parse的额外空间在import System.Environment import System.Directory import System.IO (hSetBuffering, stdin, BufferMode(NoBuffering)) *New line* import Data.List main :: IO () main = do hSetBuffering stdin NoBuffering *New line* putStrLn "Insert a string" word <- getLine putStrLn "Insert a char" char <- getChar putStrLn "Insert a position" pos <- getLine let x = (read pos :: Int) putStrLn "Adding char to list..." let newS = [(insertChar char word x)] putStrLn "Printed list: " print (newS) putStrLn "Insert file name" file <- getLine putStrLn "Adding new string to file..." add file newS insertChar :: a -> [a] -> Int -> [a] insertChar x ys 1 = x:ys insertChar x (y:ys) n = y:insertChar x ys (n-1) add :: String -> [String] -> IO () add fileName [item] = appendFile fileName item时间内运行。

Answer 5

您可以编辑代码以实现此目的而不会出错。

f = open(filename. txt)
lines = f.readlines() 

rand_line = random. randint(0,len(lines)-1) # this should make it work
print lines[rand_line]

这样索引就不会超出范围。

从txt文件中打印随机行？

5 个答案: