Python time.strftime() Function

The time.strftime() function is used to convert a struct_time object to a string according to a specified format. 

Before we look at how the function works it is worth first understanding what struct_time objects are.

struct_time objects

struct_time is a class defined in the time module, meant for representing timestamps. A struct_time object  stores a timestamp broken down into 9 basic components, i.e year, month, day of month, hour, minute, second, day of week, day of year, and dst flag (daylight savings). We can then access each of these basic components of a timestamp using the various attributes defined by the struct_time object. 

Some useful functions in the time module such as  localtime() and gmtime() converts a timestamp into a  struct_time objects.

import time

now = time.time()

#convert the timestamp 'now' in to struct_time object using localtime()
time_obj = time.localtime(now)
print(time_obj)

The work of the strftime function.

The strftime function converts a struct_time object into a formatted string.

The basic syntax for the function is as follows:

time.strftime(format, t = None)

import time

now = time.localtime()

time_obj = time.struct_time(now)

#format the timestamp with strftime()
formatted_time = time.strftime('%Y/%m/%d  %I:%M:%S %p', time_obj)

print(formatted_time)

As you have seen above, by applying correct formatting parameters, the strftime() function automatically knows how to insert the relevant  struct_time attribute values into the output string. This is useful  because it eliminates the need to perform the formatting manually.

another example

import time

time_obj = time.localtime()

formatted_date = time.strftime("%d %B %Y  %I:%M:%S %p", time_obj)
print(formatted_date)

Format strings and the parameters

In order to fully utilize the power of the strftime() function, you will need to understand how to form the format strings and what work each parameter in the format does. 

Each formatting parameter is represented by a percent sign (%) followed by a letter. Each letter represents a different part of the date and time that can be included in the format string, such as the day, month, hour, second, etc. Consider the following simplified example:

import time

format_string = "%d-%m-%Y"

#Without an argument the function uses the current timestamp
formatted_date = time.strftime(format_string)

print(formatted_date)

In the above example, the format string "%d-%m-%Y" can be broken as follows:

The following table summarizes the various format parameters