How to map month name to month number and vice versa?

Full month name to month number (e.g. January, February, etc..):

import datetime

month_name = 'January'
month_num = datetime.datetime.strptime(month_name, '%B').month

print(month_num, type(month_num))

>> 1 <class 'int'>

Partial month name to month number (e.g. Jan, Feb, etc..):

import datetime

month_name = 'Feb'
month_num = datetime.datetime.strptime(month_name, '%b').month

print(month_num, type(month_num))

>> 2 <class 'int'>

You can also format it to double-digits representation:

month_num = 3
formatted = f"{month_num:02}"

print(formatted, type(formatted))

>> 03 <class 'str'>

Month number to full month name (either double-digits representation or not, either string or int) (e.g. '01', 1, etc..):

import datetime

month_num = '04'  # month_num = 4 will work too
month_name = datetime.datetime(1, int(month_num), 1).strftime("%B")

print(month_name)

>> April

Month number to partial month name (either double-digits representation or not, either string or int) (e.g. '01', 1, etc..):

import datetime

month_num = 5  # month_num = '05' will work too
month_name = datetime.datetime(1, int(month_num), 1).strftime("%b")

print(month_name)

>> May

form month name to number
d=['JAN','FEB','MAR','April','MAY','JUN','JUL','AUG','SEP','OCT','NOV','DEC']
N=input()
for i in range(len(d)):
    if d[i] == N:
        month=(i+1)
print(month)

To get the full calendar name from the month number, you can use calendar.month_name. Please see the documentation for more details: https://docs.python.org/2/library/calendar.html

month_no = 1
month = calendar.month_name[month_no]

# month provides "January":
print(month)

Building on ideas expressed above, This is effective for changing a month name to its appropriate month number:

from time import strptime
monthWord = 'september'

newWord = monthWord [0].upper() + monthWord [1:3].lower() 
# converted to "Sep"

print(strptime(newWord,'%b').tm_mon) 
# "Sep" converted to "9" by strptime

You can use below as an alternative.

1. Month to month number:

from time import strptime

strptime('Feb','%b').tm_mon

2. Month number to month:

import calendar

calendar.month_abbr[2] or calendar.month[2]

def month_num2abbr(month):
    month = int(month)
    import calendar
    months_abbr = {month: index for index, month in enumerate(calendar.month_abbr) if month}
    for abbr, month_num in months_abbr.items():
        if month_num==month:
            return abbr
    return False

print(month_num2abbr(7))

If you don't want to import the calendar library, and need something that is a bit more robust -- you can make your code a little bit more dynamic to inconsistent text input than some of the other solutions provided. You can:

1. Create a month_to_number dictionary
2. loop through the .items() of that dictionary and check if the lowercase of a string s is in a lowercase key k.

month_to_number = {
'January' : 1,         
'February' : 2,         
'March' : 3,           
'April' : 4,              
'May' : 5, 
'June' : 6,
'July' : 7, 
'August' : 8, 
'September' : 9, 
'October' : 10, 
'November' : 11, 
'December' : 12}

s = 'jun'
[v for k, v in month_to_number.items() if s.lower() in k.lower()][0]

Out[1]: 6

Likewise, if you have a list l instead of a string, you can add another for to loop through the list. The list I have created has inconsistent values, but the output is still what would be desired for the correct month number:

l = ['January', 'february', 'mar', 'Apr', 'MAY', 'JUne', 'july']
[v for k, v in month_to_number.items() for m in l if m.lower() in k.lower()]

Out[2]: [1, 2, 3, 4, 5, 6, 7]

The use case for me here is that I am using Selenium to scrape data from a website by automatically selecting a dropdown value based off of some conditions. Anyway, this requires me relying on some data that I believe our vendor is manually entering to title each month, and I don't want to come back to my code if they format something slightly differently than they have done historically.