for ch in "john.smith@pythoninstitute.org":
    if ch == "@":
        break
    print(ch, end='')

8158311dbd29d5418d00205f9467f7ec2cc94abe
<mask token>

for ch in 'john.smith@pythoninstitute.org':
    if ch == '@':
        break
    print(ch, end='')

for ch in "john.smith@pythoninstitute.org":
    if ch == "@":
        break
    print(ch, end='')
