我怎樣才能做數學項目在Python中的列表？

Question

我有這個測試文件：

123 52 65 75 
40 58 34 8 

98 89 89 98 
45 34 29 49 

，我想借此每兩個數字，它們相乘。我有一些問題。我知道我應該做一些任務，我會從x = 0開始，以x + = 1結束一個計數器和任何事情，但我需要幫助開始。

這是我到目前爲止有：

我有一個文件，該文件的全數字，我想取文件中每三個數字加在一起，然後除以2，這裏是我的到目前爲止：

text= input('file: ') 
f = open(text, 'r') 
for line in f: 
    counter = 0 
    for n in line: 
     counter *= int(n) 
    print(counter) 

這將行中的所有數字相乘，但我只是想每兩個。我覺得我很接近但需要一些建議。

Answer 1

使用inline for。 這樣的事情？

[line[n] * line[n+1] for range(0,len(line),2)] 

Answer 2

正如皮特所說，你可以在列表理解中做到這一點。

對於初學者，我認爲for循環更容易閱讀。在你的對象上調用enumerate()會給你一個迭代器。

line = [4, 5, 7, 8] 
product = 1 
# loop_number counts up from 1 
for loop_number, value in enumerate(line, start=1): 
    print('LOOP_NUMBER_(ITERATOR)_IS: ' + str(loop_number)) 
    product *= value 
    print('PRODUCT IS NOW: ' + str(product)) 
    if loop_number % 2 == 0: 
     print('OUTPUT PRODUCT: ' + str(product)) 
     product = 1 

輸出：

LOOP_NUMBER_(ITERATOR)_IS: 1 
PRODUCT IS NOW: 4 
LOOP_NUMBER_(ITERATOR)_IS: 2 
PRODUCT IS NOW: 20 
OUTPUT PRODUCT: 20 
LOOP_NUMBER_(ITERATOR)_IS: 3 
PRODUCT IS NOW: 7 
LOOP_NUMBER_(ITERATOR)_IS: 4 
PRODUCT IS NOW: 56 
OUTPUT PRODUCT: 56 

Answer 3

我想借此每兩個數字，它們相乘。

它總是最好要發佈：

1. 你的出發數據。

   [1, 2, 3, 4] 
   
   1 * 2 => 2 
   3 * 4 => 12 
   

   ，那麼你可以這樣做：：

   import csv 
   import itertools as it 
   
   with open('data.txt', newline='') as f: 
       csv_reader = csv.reader(f, delimiter=' ') 
   
       for row in csv_reader: 
        print(row) #=> ['1', '2', '3', '4'] 
   
        every_other0 = it.islice(row, 0, False, 2) #Produces items from the row at index 0, 2, etc. 
        every_other1 = it.islice(row, 1, False, 2) #Produces items from the row at index 1, 3, etc. 
   
        while True: 
         str1 = next(every_other0, None) #if there are no more items in every_other0, return False 
         str2 = next(every_other1, None) #if there are no more items in every_other1, return False 
   
         if str1 and str2: #if either str1 or str2 is False, the condition is False 
          num1 = int(str1) 
          num2 = int(str2) 
          print("{} * {} = {}".format(num1, num2, num1*num2)) 
         else: 
          break 
   

   ---

   $ cat data.txt 
   1 2 3 4 
   5 6 7 8 
   
   ~/python_programs$ python3.4 prog.py 
   ['1', '2', '3', '4'] 
   1 * 2 = 2 
   3 * 4 = 12 
   ['5', '6', '7', '8'] 
   5 * 6 = 30 
   7 * 8 = 56 
   

2. 你想

如果你想乘數對在一起，像這樣做的實際結果

---

基於您的代碼在這裏

：

counter = 0 
for n in line: 
    counter *= int(n) 

也許你想要的東西，像下面這樣：

import operator as op 
import functools as funcs 
import csv 

with open('data.txt', newline='') as f: #opens the file and automatically closes the file when the block is exited for any reason--including if an exception occurs 
    csv_reader = csv.reader(f, delimiter=' ') 

    for row in csv_reader: 
     every_other = [int(item) for item in row[::2] ] #=> row[::2] is equivalent to row[0:len(row):2], which means get the element at index 0, then add the step, 2, to the index value, and get the next element, etc., and stop at the index len(row). 
     print(every_other) 

---

[1, 1, 1] 

---

 result = funcs.reduce(op.mul, every_other) #multiply all the numbers in every_other together, reducing them to one number 
     print(result) 

---

1 

---

 every_other = [int(item) for item in row[1::2] ] #=> row[1::2] is equivalent to row[1:len(row):2], which means start at index 1 and stop at a the end of row, and get the element at index 1; add the step, 2, to the index value, and get the element at that index, etc. 
     print(every_other) 

---

[2, 2, 2] 

---

 result = funcs.reduce(op.mul, every_other) 
     print(result) 

---

8