Python calendar with loops - python-3.x

Question

days = int(input("Enter number of days: "))
day_of_week = input("The first day of the week: ")
print("{:>3}{:>3}{:>3}{:>3}{:>3}{:>3}{:>3}".format("S","M","T","W","Th","F","S"))
for d in range(1, days + 1):
print("{:3}".format(d),end="")
if (d % 7 == 0):
print()
Here's my output:
I'm confused... What should I add so that the first day of the week is my input's?

Answer 1

Below is one solution that actually uses the start day that you enter. You'll notice a couple of other improvements as well, specifically:
using an array of days for validation (I've made them match my sensibilities of two characters each but they'll work with the same entries you originally had);
using that same array for figuring out where the month should start;
also using it for simplifying the heading output;
validates the number of days to output;
adds a final newline output; and
uses f-strings for formatting (I prefer this because it localises the value to where it should be, rather than way out to the right somewhere in the format() parameter area, where you have to go searching for it).
The code is:
# Valid day list, adjust as necessary.
day_list = ["Su", "Mo", "Tu", "We", "Th", "Fr", "Sa"]
# Get days in month, with validation.
days = -1
while days < 1 or days > 31:
try:
days = int(input("Enter number of days: "))
if days < 28 or days > 31:
days = -1
except ValueError:
days = -1
# Get starting day, with validation.
start_day = ""
while start_day not in day_list:
start_day = input(f"The first day of the week ({', '.join(day_list)}): ")
# Output heading line.
for day in day_list:
print(f"{day:>3}", end="")
print()
# Pad with spaces in first week if needed.
start_pos = day_list.index(start_day)
for _ in range(start_pos):
print(" ", end="")
# Output each day, wrapping to new week if needed.
for day in range(1, days + 1):
if (start_pos != 0 and start_pos % 7 == 0):
print()
print(f"{day:3}", end="")
start_pos += 1
# Output final newline.
print()
A couple of sample runs:
Enter number of days: 27
Enter number of days: 32
Enter number of days: 28
The first day of the week (Su, Mo, Tu, We, Th, Fr, Sa): blah
The first day of the week (Su, Mo, Tu, We, Th, Fr, Sa): Mo
Su Mo Tu We Th Fr Sa
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28
Enter number of days: 30
The first day of the week (Su, Mo, Tu, We, Th, Fr, Sa): Su
Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30
Enter number of days: 29
The first day of the week (Su, Mo, Tu, We, Th, Fr, Sa): Sa
Su Mo Tu We Th Fr Sa
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29

Answer 2

days_of_week = ["S","M","T","W","Th","F","St"]
days = int(input("Enter number of days: "))
day_of_week = input("The first day of the week: ")
index = days_of_week.index(day_of_week)
new_days_of_week = days_of_week[index:]+days_of_week[:index]
print("{:>3}{:>3}{:>3}{:>3}{:>3}{:>3}{:>3}".format(*new_days_of_week))
for d in range(1, days + 1):
print("{:3}".format(d),end="")
if (d % 7 == 0):
print()
Output
Enter number of days: 31
The first day of the week: Th
Th F St S M T W
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31