如何使用循環在 csv python 中寫入多行

Question

嗨，我正在使用這種方法從 csv 文件中寫入 csv 文件，這是一個散列代碼，但我只收到 output 中的最后一行，如何將每一行添加到前一行？

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

Answer 1

其他答案建議用'a'替換'w' ，使用csv.writer時沒有必要這樣做。 每次運行程序時，它還可能使您的文件增長。

與其重新打開和關閉 relut3.txt，不如保持打開狀態並僅使用一位編寫writer

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as result_file:
    result_writer = csv.writer(result_file)  # only create this once
    
    with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
        file = csv.reader(f)
        for row in file :
            a = row[0]
            b = d[row[1]]
            result = (a , b)

            result_writer.writerow(result)  # use the already created writer

Answer 2

您的代碼正在向文件寫入一行，然后再次打開文件並將下一行寫入程序的全部內容。 所以在第二次循環中只有第二行會在文件中。

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'a') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

打開文件然后將所有內容寫入其中可能會更好：

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    with open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as f2:
        file2 = csv.writer(f2)
        for row in file :
            a = row[0]
            b = d[row[1]]
            result = (a , b)
            
            file2.writerow(result)

Answer 3

我不能自己運行這個，因為你的數據不包括在內。

但是，我認為你的問題是with open('/Users/MJ-Mac/Desktop/result3.txt', 'w')有“w”標志——代表“寫”——所以你的數據是被覆蓋，您可能需要“附加”的“a”標志，以便每一行都將附加到您正在導出的數據中。

import hashlib
import csv
d = dict()
result = ()
for i in range(0 , 9999) :
    n = hashlib.sha256(str(i).encode())
    d[n.hexdigest()] = str(i)
with open('/Users/MJ-Mac/Desktop/karname.txt') as f:
    file = csv.reader(f)
    for row in file :
        a = row[0]
        b = d[row[1]]
        result = (a , b)
        with open('/Users/MJ-Mac/Desktop/result3.txt', 'a') as f2:
            file2 = csv.writer(f2)
            file2.writerow(result)

Answer 4

一次打開輸入文件和 output 文件更容易：

with open('/Users/MJ-Mac/Desktop/karname.txt') as f, open('/Users/MJ-Mac/Desktop/result3.txt', 'w') as f2:
    output = csv.writer(f2)
    for row in csv.reader(f):
        output.writerow([row[0], d[row[1]])