Swift and Python side by side

Introduction

Lets print “Hello, world!”

$ python
print("Hello, world!")

$ swift
1> print("Hello, world!")
Hello, world!

Exactly same code!. What happens if I use single-quoted string?

$ python
print('Hello, world!')

$ swift
1> print('Hello, world!')
error: repl.swift:1:7: error: single-quoted string literal found, use '"'
print('Hello, World!')
      ^~~~~~~~~~~~
      "Hello, World!"

Notes:

1. Single quotes do not work in Swift
2. The error messages in Swift are helpful! It even suggests the correct quoting in this case.

Strings

How about string formatting?

print('%s had %d %s' % ('mary', 10, 'apples'))

print(String(format: "%@ had %d %@", "mary", 10, "apples"))
 
mary had 10 apples

The %@ is weird; which is defined here

But, Swift’s native string formatting is more on the lines of

name = 'Mary'
count = 10
fruit = 'Apples'
print('%(name)s had %(count)d %(fruit)s' % locals())
 
Mary had 10 Apples

Swift uses \(variable) for string interpolation.

let name = "Mary"
let count = 10
let fruit = "Apples"
print("\(name) had \(count) \(fruit)")

Control flow

Enough Strings, lets do loops:

for i in range(2):
    print("Hello!")
 
Hello!
Hello!

The curly-braces are a’coming! Brace for it.

for i in 0..<2 {
    print("Hello!")
}
 
Hello!
Hello!

I actually think this range operator 0..<2 is very explicit about the number generated to be less than 2, which is a good thing.