将字典中的所有内容都转换为小写，然后对其进行过滤？

Question

import pandas as pd
import nltk
import os

directory = os.listdir(r"C:\...")

x = []
num = 0

for i in directory:
    x.append(pd.read_fwf("C:\..." + i))
    x[num] = x[num].to_string()

所以，一旦我的目录中的每个文件都有一个字典 x = [ ] 由 read_fwf 填充：

我想知道如何让每个字符都是小写的。我无法理解语法及其如何应用于字典。
我想定义一个过滤器，我可以用它来计算这个新定义的词典中的单词列表，例如，

list = [公共汽车、汽车、火车、飞机、电车……]

编辑：快速无关的问题：

pd_read_fwf 是阅读 .txt 文件的最佳方式吗？如果没有，我还能用什么？

非常感谢任何帮助。谢谢

编辑 2：我想要的示例数据和输出：

样本：

The Horncastle boar's head is an early seventh-century Anglo-Saxon ornament depicting a boar that probably was once part of the crest of a helmet. It was discovered in 2002 by a metal detectorist searching in the town of Horncastle, Lincolnshire. It was reported as found treasure and acquired for £15,000 by the City and County Museum, where it is on permanent display.

所需输出 - 将大写的所有内容更改为小写：

the horncastle boar's head is an early seventh-century anglo-saxon ornament depicting a boar that probably was once part of the crest of a helmet. it was discovered in 2002 by a metal detectorist searching in the town of horncastle, lincolnshire. it was reported as found treasure and acquired for £15,000 by the city and county museum, where it is on permanent display.

Answer 1

我想你要找的是字典理解：

# Python 3
new_dict = {key: val.lower() for key, val in old_dict.items()}

# Python 2
new_dict = {key: val.lower() for key, val in old_dict.iteritems()}

items()/iteritems() 为您提供字典中表示的 (keys, values) 的元组列表（例如 [('somekey', 'SomeValue'), ('somekey2', 'SomeValue2')]）

推导式遍历每一对，在此过程中创建一个新字典。在 key: val.lower() 部分，你可以做任何你想创建新字典的操作。

Answer 2

您根本不需要使用 pandas 或字典。只需使用 Python 的内置 open() 函数：

# Open a file in read mode with a context manager
with open(r'C:\path\to\you\file.txt', 'r') as file:
    # Read the file into a string
    text = file.read()
    # Use the string's lower() method to make everything lowercase
    text = text.lower()
    print(text)

    # Split text by whitespace into list of words
    word_list = text.split()
    # Get the number of elements in the list (the word count)
    word_count = len(word_list)
    print(word_count)

如果你愿意，可以按相反的顺序进行：

# Open a file in read mode with a context manager
with open(r'C:\path\to\you\file.txt', 'r') as file:
    # Read the file into a string
    text = file.read()
    # Split text by whitespace into list of words
    word_list = text.split()
    # Use list comprehension to create a new list with the lower() method applied to each word.
    lowercase_word_list = [word.lower() for word in word_list]
    print(word_list)

为此使用上下文管理器很好，因为它会在文件超出范围时自动为您关闭文件（从 with 语句块中取消制表符）。否则你将不得不使用 file.open() 和 file.read().

我认为使用上下文管理器还有其他一些好处，但如果我错了，请有人纠正我。

将字典中的所有内容都转换为小写，然后对其进行过滤？

Convert everything in a dictionary to lower case, then filter on it?

ordereddictionary

lowercase

python-3.x