How does python’s time.time() method work?

by

In (the current) CPython time.time() calls
floattime(NULL) which calls
_PyTime_gettimeofday_info() which calls
pygettimeofday()
where pygettimeofday() may use GetSystemTimeAsFileTime(), clock_gettime(CLOCK_REALTIME), gettimeofday() functions depending on the platform.

Unrelated: time.time() returns “seconds since the epoch”. It is POSIX time on most systems supported by Python (Linux, OS X, Windows). POSIX timestamp is not the number of elapsed SI seconds since 1970-01-01T00:00:00Z (Epoch). Though it is very close (within 0.000003% counting from Epoch). It counts the number of non-leap SI seconds or the number of UT1 (mean-solar) seconds.

UTC is not a linear time scale relative to TAI, GPS time scales (see the picture). You won’t get the exact elapsed SI seconds due to leap seconds (UTC is kept within ±0.9 seconds of UT1 (Earth rotation)). See also, Is a day always 86,400 epoch seconds long?

Some OSes can be configured to use non-POSIX “right” zoneinfo. time.time() is not required to return POSIX timestamp in this case. “right” timezone counts leap seconds and therefore the difference between “right” timestamps and POSIX timestamps is not constant e.g., it will increase in July 2015 due to the introduction of the positive leap second.

In principle, “the epoch” may differ from POSIX Epoch, though Python doesn’t support such systems.

More Related Contents:

  1. %d format: a number is required not list
  2. Should MySQL have its timezone set to UTC?
  3. Set scientific notation with fixed exponent and significant digits for multiple subplots
  4. connected component labeling in python
  5. cv2.imread always returns NoneType
  6. unknown error: call function result missing ‘value’ for Selenium Send Keys even after chromedriver upgrade
  7. Is it always a good idea to store time in UTC or is this the case where storing in local time is better?
  8. How to get current time in python and break up into year, month, day, hour, minute?
  9. How to control the download of files with Selenium + Python bindings in Chrome
  10. Why does Java’s java.time.format.DateTimeFormatter#format(LocalDateTime) add a year?
  11. vscode import error for python module
  12. GAE ndb design, performance and use of repeated properties
  13. appcfg.py not working in command line
  14. Pip does not work after upgrade to ubuntu-16.10
  15. Using Multiple Databases with django
  16. How do I install Keras and Theano in Anaconda Python on Windows?
  17. Pyspark filter dataframe by columns of another dataframe
  18. ImportError when importing certain modules from SciPY
  19. Android get Current UTC time [duplicate]
  20. How can I pass arguments into redirect(url_for()) of Flask?
  21. AWS python lambda function:No module named requests
  22. Pandas Bad Lines Warning Capture
  23. How to convert from UTC to local time in C?
  24. Using my own corpus instead of movie_reviews corpus for Classification in NLTK
  25. Move and replace if same file name already exists?
  26. Retrieve S3 file as Object instead of downloading to absolute system path
  27. Quick implementation of character n-grams for word
  28. Using scipy curve_fit for a variable number of parameters
  29. SparkSQL on pyspark: how to generate time series?
  30. String formatting [str.format()] with a dictionary key which is a str() of a number

Leave a Comment