Python：如何从文件中读取数据并与其进行数学运算

Question

如何读取文件输入，然后说出是否不是一年，那么不要使用该数据。如果是一年（4位数字），那么通过简单的数学计算是否是闰年。

我在问更多，所以如何用文件来做到这一点。我可以正常地进行数学运算，但是当文件涉及到时，我不知道文件是如何工作的。

编辑 此外，我如何做单独的函数来检查输入是否是数字，以及另一个函数来计算它是否是闰年。

file_name_one =输入（ “第一文件名：”） file_stream =开放（file_name_one， “R”）

用于线在file_stream： year_str =行[：4] 年= 0 leap_year = 0 div_4 = 0 div_100 = 0 div_400 = 0

if year_str.isdigit(): # test if year_str is an integer 
    year = int(year_str) 
    if year%4 == 0:   # check if the year is a leap year 
     div_4 = 1 
    if year%100 == 0: 
     div_100 = 1 
    if year%400 == 0: 
     div_400 = 1 
    if div_4 == 1 & div_100 == 0: 
     print (line[:4], "is a leap year") 
    if div_4 == 1 & div_100 == 0 & div_400 == 1: 
     print (line[:4], "is a leap year") 
    div_4 = 0 
    div_100 = 0 
    div_400 = 0 

Answer 1

，如果我知道你想从文件中读取，是吗？

意愿的是，它真的很容易：

with open("filename","r") as file : 
    input = file.read() 

Answer 2

如果文件被命名为“foo.txt的”，如果你是在文件的同一目录下，则是这样的：

file_stream = open("foo.txt",'r') 
for line in file_stream: 

    # as suggested in the comment, it might be a good idea to print the line, 
    # just so you know what the file looks like 
    print line 

    # the variable line is a string. depending on the formatting of the file, 
    # something along these lines might work: 

    year_str = line[:4] 
    if year_str.isdigit(): # test if year_str is an integer 
     year = int(year_str) 
     if not year%4:   # check if the year is a leap year 
      # 
      print "%s is a leap year %s"%year 
      .... 

Answer 3

如果你需要读取多行数据，readlines（）是一个很好的函数。试试这个：

f = open("myfile.txt", "r") 
lines = f.readlines() 
for line in lines: 
    print line 

修改第四行来检查你的数据是否看起来像一年。

Answer 4

为您更新的问题：

import re 

def check_is_year(year): 
    # implement as per other answers 
    return True # if `year` is valid, else return False 

def check_is_leap(year): 
    # implement as you will 
    return True # if `year` is a leap year, else False 

with open("foo.txt") as f: 
    years = [year for year in re.findall("/b/d{4}/b",f.read()) if check_is_year(year)] 
    for year in years: 
     if check_is_leap(year): 
      # do whatever you want.