Python: convert datetime format to another

Question

So i have this kind f format:

'%Y-%m-%d %H:%M:%S.%f'

date_time = datetime.now()

Ouput

'2019-04-15 07:52:14.211697'

And i want to change is into this format: '%Y-%m-%d %H:%M:%S,%f'

This is what i have try:

time = datetime.strptime(str(date_time), '%Y-%m-%d %H:%M:%S,%f')

And this is the error :

ValueError: time data '2019-04-15 07:52:14.211697' does not match format '%Y-%m-%d %H:%M:%S,%f'

Edit

So i have this string :

    maches = regex.findall(
        '[0-9]{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[1-2][0-9]|3[0-1]) (?:2[0-3]|[01][0-9]):[0-5][0-9]:[0-5][0-9],[0-9][0-9][0-9]',
        line)

match[0] = '2019-03-13 17:35:35,855'

And i want to convert it to Datetime :

time = datetime.strptime(maches[0], '%Y-%m-%d %H:%M:%S,%f')

And this returned another format :

2019-03-13 17:35:35.855000

Why ?

Answer 1

You want to use strftime:

str_time = datetime.strftime(date_time, '%Y-%m-%d %H:%M:%S,%f')

A quick comparison of strftime and strptime :

strftime() is used to convert a datetime object to a string

strptime() is used to convert a date string to a datetime object

Also here's a good resource in the documentation describing the differences: strftime() and strptime() Behavior

Response to Question Edit

In response to your edit strptime takes a string date and converts it into a datetime object. The format you pass to it just tells it how to parse the string to datetime. It does not dictate it's print format. You are calling print on a datetime object in this case so the output is dictated by the __str__ method on the datetime object.

If you want to print it in a certain way pass it to strftime with the format you want to output it as:

obj_time = datetime.strptime(maches[0], '%Y-%m-%d %H:%M:%S,%f')
print(datetime.strftime(obj_time , '%Y-%m-%d %H:%M:%S,%f'))

Answer 2

Use strftime.

date_time = datetime.now()
print(date_time)
print(datetime.strftime(date_time, '%Y-%m-%d %H:%M:%S,%f'))

2019-04-15 10:26:08.637630
2019-04-15 10:26:08,637630

Answer 3

使用此格式，您将获得以下格式：'％Y-％m-％d％H：％M：％S，％f'

print '{:%Y-%m-%d %H:%M:%S.%f}'.format(date_time)