Python 3.6中str()函数作用及str(word.strip(), encoding='utf-8')功能咨询

Hey there! Let's tackle your Python questions clearly and directly:

In Python 3.6 (and all Python 3 versions), the str() function serves two core purposes:

• Convert non-string objects to string type: It turns integers, floats, booleans, or even custom objects into human-readable string representations. For example:
  • str(42) returns "42"
  • str(3.14) returns "3.14"
  • str(False) returns "False"
• Decode bytes to string (less common): If you pass a bytes object as the first argument, specifying an encoding like "utf-8" converts those raw bytes into a proper Unicode string. This works exactly like calling .decode(encoding) on the bytes object (e.g., str(b'hello', 'utf-8') is equivalent to b'hello'.decode('utf-8')).

Let's break this line down piece by piece:

1. word.strip(): This removes whitespace characters (spaces, tabs, newlines, etc.) from the start and end of word. For example, if word was " hello! ", word.strip() would output "hello!".
2. str(..., encoding="utf-8"): This syntax is a holdover from Python 2 (where str and bytes were interchangeable), which is probably why you struggled to find clear answers online. In Python 3:
   • If word.strip() returns a bytes object, this call decodes those bytes into a UTF-8 encoded string. For instance, if word was b' python rocks! ', word.strip() gives b'python rocks!', and str(..., encoding="utf-8") turns that into the string "python rocks!".
   • If word.strip() is already a string (str type), this will throw a TypeError—Python 3's str() doesn't accept an encoding argument when the input is a string.

For Python 3, the cleaner, more idiomatic alternatives are:

• If working with bytes: Use word.strip().decode("utf-8")
• If working with strings: Just use word.strip() (no need for the str() wrapper at all)

内容的提问来源于stack exchange，提问作者Meraj