Great question! Let’s break down their key distinctions and clarify their relationship to UTC time:

Core Similarity: Both Are UTC-Based #

First off—yes, both do represent the current UTC time!

• time.time() calculates seconds since the Unix Epoch (1970-01-01 00:00:00 UTC), so its value is inherently tied to UTC.
• datetime.datetime.utcnow() explicitly returns the current UTC date and time, ignoring your local system’s timezone.

Key Differences #

1. Return Type #

• time.time() spits out a floating-point number (e.g., 1700000000.123456), where the integer part is whole seconds since the epoch, and the decimal part represents milliseconds/microseconds (depending on your system’s precision).
• datetime.datetime.utcnow() returns a structured datetime object (e.g., datetime.datetime(2023, 11, 14, 13, 20, 5, 678901)), which encapsulates year, month, day, hour, minute, second, and microsecond as individual properties you can access directly (like .year, .microsecond).

2. Precision & Usage #

• time.time() shines when you need a lightweight, numeric timestamp: ideal for calculating time differences (e.g., end_time - start_time), storing timestamps in databases, or interacting with systems that use Unix time. Its precision is typically microsecond-level, though floating-point rounding can introduce tiny, negligible errors.
• datetime.utcnow() is better for date-time manipulation and human-readable output. You can easily format it into strings (e.g., utc_time.strftime("%Y-%m-%d %H:%M:%S")), perform arithmetic (e.g., utc_time + datetime.timedelta(hours=3)), or extract specific time components without parsing a numeric value. One caveat: in Python 3.2+, consider using datetime.datetime.now(datetime.timezone.utc) instead—it returns a timezone-aware datetime object, whereas utcnow() gives a "naive" object (no explicit timezone attached, even though it’s UTC).

3. Readability & Structure #

• time.time() is a raw number—you’ll need to convert it to a datetime object if you want to interpret it as a human-readable date. For example:

  import time
  from datetime import datetime
  
  timestamp = time.time()
  utc_datetime = datetime.utcfromtimestamp(timestamp)
  

• datetime.utcnow() is immediately human-interpretable via its attributes or formatting methods, no conversion needed.

内容的提问来源于stack exchange，提问作者Knot