如何使用Python 3中的readlines读取由空格分隔的整数输入文件?
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我需要读取一个包含一行整数(13 34 14 53 56 76)的输入文件(input.txt),然后计算每个数字的平方和。
这是我的代码:
# define main program function
def main():
print("
This is the last function: sum_of_squares")
print("Please include the path if the input file is not in the root directory")
fname = input("Please enter a filename : ")
sum_of_squares(fname)
def sum_of_squares(fname):
infile = open(fname, 'r')
sum2 = 0
for items in infile.readlines():
items = int(items)
sum2 += items**2
print("The sum of the squares is:", sum2)
infile.close()
# execute main program function
main()
如果每个数字都在它自己的行上,它可以正常工作。
但是,当所有数字都在一个由空格分隔的行上时,我无法弄清楚如何做到这一点。在那种情况下,我收到错误:ValueError: invalid literal for int() with base 10: '13 34 14 53 56 76'
您可以使用file.read()
获取字符串,然后使用str.split
按空格分割。
您需要先将每个数字从string
转换为int
,然后使用内置的sum
函数计算总和。
另外,您应该使用with
语句为您打开和关闭文件:
def sum_of_squares(fname):
with open(fname, 'r') as myFile: # This closes the file for you when you are done
contents = myFile.read()
sumOfSquares = sum(int(i)**2 for i in contents.split())
print("The sum of the squares is: ", sumOfSquares)
输出:
The sum of the squares is: 13242
您正在尝试将包含空格的字符串转换为整数。
你想要做的是使用split方法(这里,它将是items.split(' ')
,它将返回一个字符串列表,包含数字,这次没有任何空格。然后你将遍历这个列表,将每个元素转换为一个int作为你已经在尝试做了。
我相信你会发现下一步该做什么。 :)
这是一个简短的代码示例,使用更多pythonic方法来实现您要执行的操作。
# The `with` statement is the proper way to open a file.
# It opens the file, and closes it accordingly when you leave it.
with open('foo.txt', 'r') as file:
# You can directly iterate your lines through the file.
for line in file:
# You want a new sum number for each line.
sum_2 = 0
# Creating your list of numbers from your string.
lineNumbers = line.split(' ')
for number in lineNumbers:
# Casting EACH number that is still a string to an integer...
sum_2 += int(number) ** 2
print 'For this line, the sum of the squares is {}.'.format(sum_2)
您可以尝试使用split()函数在空间上拆分项目。
来自文档:例如,' 1 2 3 '.split()
返回['1', '2', '3']
。
def sum_of_squares(fname):
infile = open(fname, 'r')
sum2 = 0
for items in infile.readlines():
sum2 = sum(int(i)**2 for i in items.split())
print("The sum of the squares is:", sum2)
infile.close()
保持简单,不需要任何复杂的事情。这是一个评论一步一步的解决方案:
def sum_of_squares(filename):
# create a summing variable
sum_squares = 0
# open file
with open(filename) as file:
# loop over each line in file
for line in file.readlines():
# create a list of strings splitted by whitespace
numbers = line.split()
# loop over potential numbers
for number in numbers:
# check if string is a number
if number.isdigit():
# add square to accumulated sum
sum_squares += int(number) ** 2
# when we reach here, we're done, and exit the function
return sum_squares
print("The sum of the squares is:", sum_of_squares("numbers.txt"))
哪个输出:
The sum of the squares is: 13242
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