Python列表写入文本文件的最优方法及常见报错解决

Hey there! Let's walk through what's wrong with each of your writing methods, then show you the cleanest ways to get this done—including a much simpler approach using pandas since you already imported it.

First, a quick note on your extraction code #

Wait, one thing to double-check: i.split()[3] grabs the 4th column (since Python uses 0-based indexing). If you actually need the 3rd column, you should use i.split()[2] instead. Just wanted to flag that to avoid column mix-ups!

Why each method failed #

1. Method 1: The csv.writer.writerows() expects a list of rows, where each row is a list of columns. When you pass x (a list of strings), it treats each string as a row of individual characters (since strings are iterable). With delimiter='\n', this splits each character onto its own line, which is why you see split-up digits. You could fix this by wrapping each item in a list (writer.writerows([[item] for item in x])), but using csv for this is overkill—plain file writing is simpler.

2. Method 2: You tried calling x.write(...), but x is a list, not a file object. The write() method belongs to open file handles, not lists. You need to open a file first and call write() on that file object instead.

3. Method 3: str(x) converts your entire list into a single string (e.g., ['1.23', '4.56'] becomes "['1.23', '4.56']"). Writing this directly puts everything on one line with commas, which isn't what you want for a single-column file.

4. Method 4: Here you're calling i.write(...) where i is a string from your list. Strings don't have a write() method—again, this is a method for file objects, not the data you're writing.

5. Method 5: The variable number isn't defined anywhere in your code. You probably meant to loop through the items in x and write each one, but forgot to reference the loop variable.

Optimal Solutions #

Option 1: Plain Python (no pandas)

This is straightforward and efficient for small to medium files:

import os

# First, fix the extraction (adjust index to 2 if you need the 3rd column)
myfile = "your_input_file.txt"
output_path = "x.txt"
x = []

# Use with-statement to auto-close the file (safer than manual close())
with open(myfile, "r") as f:
    for line in f:
        stripped_line = line.strip()
        if stripped_line:  # Skip empty lines
            parts = stripped_line.split()
            x.append(parts[3])  # 4th column; use parts[2] for 3rd

# Write to output file efficiently
with open(output_path, "w") as f:
    # Join all items with newlines, add a final newline for clean formatting
    f.write("\n".join(x) + "\n")

# Or if you prefer line-by-line writing (slower for large files but readable)
# with open(output_path, "w") as f:
#     for item in x:
#         f.write(f"{item}\n")

Option 2: Use pandas (way simpler for multi-column tasks)

Since you already imported pandas, let's leverage it—especially useful if you need to write all 7 columns to separate files later:

import pandas as pd
import os

myfile = "your_input_file.txt"
# Read the space-separated file (no headers)
df = pd.read_csv(myfile, sep="\s+", header=None)

# Write the 4th column (index 3) to x.txt (adjust to 2 for 3rd column)
df[3].to_csv("x.txt", index=False, header=False)

# Bonus: Write ALL 7 columns to separate files in one go!
for col_index in range(df.shape[1]):
    # Name files like column1.txt, column2.txt, etc.
    output_file = f"column{col_index + 1}.txt"
    df[col_index].to_csv(output_file, index=False, header=False)

This handles edge cases like inconsistent spacing between columns, empty lines, and formatting automatically—saving you way more time than debugging manual splits and writes.

内容的提问来源于stack exchange，提问作者FabioSpaghetti