Python thousands separators - Don't use commas and use underscores

You can format an Python interger as a string with thousands separators using the format().

s1 = '{:,}'.format(31415)
s2 = '{:,}'.format(123456789)
s3 = '{:,}'.format(10000000000)

print(s1)  # 31,415
print(s2)  # 123,456,789
print(s3)  # 10,000,000,000

The expression of Python intergers with thousands separators

a = 31415
b = 1, 000
c = 123, 456, 789

print(a)  # 31415
print(b)  # (1, 0)
print(c)  # (123, 456, 789)

Python integers can't contain separator commas and 1, 000 is regarded as a tuple of (1, 0). A Comma works as a separator. An underscore works as thousands separators.

b = 1_000
c = 123_456_789

print(b)  # 1000
print(c)  # 123456789

print(type(b))  # <class 'int'>
print(type(c))  # <class 'int'>

The underscores don't necessarily separate thousands.

b = 10_00
c = 1234_56789

print(b)  # 1000
print(c)  # 123456789

print(type(b))  # <class 'int'>
print(type(c))  # <class 'int'>