Python 日期與時間

下面列出 Python 中時間處理範例
需注意的是，Python 這邊即使是不同套件下
timestamp 精確值 大多都是到 微秒 ，
且回傳的是 秒為整數單位，小數點後再接6~7位數
主要使用的套件是 time , datetime , calendar

當使用 time module 時需注意 struct_time 這個 meta class，是不同可表現時間的不同 types 的轉換媒介
當使用 datetime module 時需注意 <class 'datetime.datetime'> 這個 class，是不同可表現時間的不同 types 的轉換媒介

References :

• datetime: 時間區間計算
• calendar: 日期日曆相關
• pytz: Time Zone
• dateutil, https://dateutil.readthedocs.io/en/stable/

Mindmap of time module

Menu Links

主題		套件
time 取微秒	UTC time/0時區	time
datetime 取微秒	UTC	datetime
millisecond	取毫秒, 微秒	time
struct_time	拆解後的每個時間單位	calendar, time
String to Date
Float to Date		datetime
Date Formatting : Date to String	from datetime to String	datetime
Python Time Zone		datetime, pytz

time package 取微秒  

• Coordinated Universal Time: UTC time, 世界協調時間

import time
current_timestamp = time.time() # microsecond, <class 'float'>
print("Timestamp:", current_timestamp)

# Timestamp: 1715152590.437168

datetime package 取微秒  

• datetime.datetime.now()
• datetime.datetime.now(timezone)
• datetime.datetime.utcnow()

import datetime
current_datetime = datetime.datetime.now() # <class 'datetime.datetime'>
print(current_datetime)
timestamp = current_datetime.timestamp() # microsecond, <class 'float'>
print("Timestamp:", timestamp)

# 2024-05-08 16:04:50.940161
# Timestamp: 1715155490.940161

import datetime
utc_datetime = datetime.datetime.utcnow()
utc_timestamp = utc_datetime.timestamp()
print("UTC Timestamp:", utc_timestamp)

* Structure Time  

• GMT Greenwich Mean Time: 格林威治標準時間 time.gmtime()
• Loacal Time: time.localtime()
• struct_time 類別將時間拆解為:
  • tm_isdst: 夏令時間調整
  • tm_year, tm_mon, tm_mday,
  • tm_hour, tm_min, tm_sec,
  • tm_wday, tm_yday

import time
import calendar
time_tuple = time.gmtime() # <class 'time.struct_time'>
print("Time Structure:", time_tuple)
timestamp = calendar.timegm(time_tuple) # <class 'int'>
print("Timestamp:", timestamp)

# Time Structure: time.struct_time(tm_year=2024, tm_mon=5, tm_mday=8, tm_hour=7, tm_min=54, tm_sec=13, tm_wday=2, tm_yday=129, tm_isdst=0)
# Timestamp: 1715154853

Float to Date, Date to String : by datetime module  

import datetime
timestamp = 1715155490.940161  # Example timestamp
datetime_object = datetime.datetime.fromtimestamp(timestamp)

print(type(datetime.datetime)) # <class 'type'>
print(type(datetime_object)) # <class 'datetime.datetime'>
print("Datetime:", datetime_object)

formatted_string = datetime_object.strftime("%Y-%m-%d %H:%M:%S")
print(type(formatted_string)) # <class 'str'>
print("Formatted Datetime:", formatted_string)

Millisecond, Microsecond  

import time
current_timestamp = time.time() # <class 'float'>, 秒為單位, 精確至(小數下7位數)?
current_timestamp_milli = int(time.time() * 1000) # 轉毫秒, 去小數點後尾數
current_timestamp_sec = int(time.time()) # 取秒, 直接去小數點後尾數

print("Timestamp in microseconds:", current_timestamp)
print("Timestamp in milliseconds:", current_timestamp_milli)
print("Timestamp in Seconds:", current_timestamp_sec)

String to Date  

• String to time_struct
• time_struct to float
• float to time_struct
• time_struct formatting

date_string = '2024-05-08 10:11:12'
struct_time = time.strptime(date_string, "%Y-%m-%d %H:%M:%S") # <class 'time.struct_time'>
print(type(struct_time))  #<class 'time.struct_time'>

float_time = time.mktime(struct_time)
print(type(float_time)) #<class 'float'>

second_time = int(float_time) # truncate to sec
print(second_time) # 1715134272


struct_time_from_sec = time.localtime(second_time) # sceond to  struct_time
struct_time_from_sec_gm = time.gmtime(second_time) # 格林威治時間 (time.localtime -8hr)
print(type(struct_time_from_sec))  #<class 'time.struct_time'>


date2 = time.strftime( "%Y-%m-%d %H:%M:%S", struct_time_from_sec) # struct_time to String
print(date2) # 2024-05-08 10:11:12

Python Time Zone  

import datetime
import pytz
# Define the timezone
desired_timezone = pytz.timezone('America/New_York')
# Create a datetime object with the desired timezone
datetime_with_timezone = datetime.datetime.now(desired_timezone)
# Convert the datetime object to a timestamp
timestamp = datetime_with_timezone.timestamp()
print("Timestamp with Different Timezone:", timestamp)

time module

default UTC time
time_string = time.asctime(struct_time) : 將 struct_time 轉成 asc format : ex, Sun May 27 01:05:27 2018
asc_time_string = time.ctime(float) : 把浮點數轉成 asc time
struct_time = time.gmtime(num)
struct_time = time.localtime(num) (UTC+8)
float= time.mktime( struct_time )
formatted_string = datetime_object.strftime("%Y-%m-%d %H:%M:%S") # by instance
formatted_string = time.strftime(format, struct_time)
struct_time= time.strptime(formatted_string, format)
float = time.time() # UTC time
time.tzset() # 依據環境變數設定值，reset 程式時間