读取字典文件问题：实现公司名称与股票代码互查函数求助

Hey there! Let's get those two lookup functions working for you, plus tweak your existing tickers_to_dict to handle small edge cases (like leftover newline characters) that might break your lookups.

Step 1: Fix the tickers_to_dict Function #

Your original code is close, but when using readlines(), each line includes a trailing newline (\n) which will get stuck in your ticker values. Let's fix that and also use Python's with statement to safely handle file closing:

def tickers_to_dict(filename):
    ticker_dict = {}
    # Use 'with' to auto-close the file after reading
    with open(filename, 'r') as bestand:
        for line in bestand:
            line = line.strip()  # Remove newlines and extra whitespace
            if not line:  # Skip empty lines if any exist
                continue
            # Split into name and symbol, then strip any leftover whitespace
            company_name, ticker_symbol = line.split(':')
            ticker_dict[company_name.strip()] = ticker_symbol.strip()
    return ticker_dict

Step 2: Implement name_to_symbol #

This one’s straightforward—your dictionary already maps company names to ticker symbols directly. We’ll use the get() method to safely handle cases where the company name isn’t found:

def name_to_symbol(name, ticker_dict):
    # Return the symbol if the name exists, else a fallback message
    return ticker_dict.get(name, "Company name not found")

Step 3: Implement symbol_to_name #

For this reverse lookup, we need to iterate through the dictionary’s items to find which company name matches the given symbol. For small datasets like yours, this is totally efficient:

def symbol_to_name(symbol, ticker_dict):
    for company_name, ticker_symbol in ticker_dict.items():
        if ticker_symbol == symbol:
            return company_name
    # Fallback if the symbol doesn't exist
    return "Ticker symbol not found"

Test the Full Workflow #

Here’s how you can use these functions to match your expected output:

# Load the ticker data from the file
ticker_data = tickers_to_dict('ticker_symbol.txt')

# Test name-to-symbol lookup
user_company = input("Enter Company name: ")
print(f"Ticker symbol: {name_to_symbol(user_company, ticker_data)}")

# Test symbol-to-name lookup
user_symbol = input("Enter Ticker symbol: ")
print(f"Company name: {symbol_to_name(user_symbol, ticker_data)}")

Quick Notes: #

• The .strip() calls handle any accidental spaces in your input file (e.g., if a line has YAHOO : YHOO instead of YAHOO:YHOO).
• Using with open(...) is a Python best practice—it ensures the file is closed automatically, even if an error occurs.
• For larger datasets, you could pre-create a reversed dictionary (symbol_to_name_map = {v: k for k, v in ticker_dict.items()}) to make reverse lookups instant, but that’s overkill for your current data.

内容的提问来源于stack exchange，提问作者programmer_66