Concatenate and Format Strings

Concatenation joins strings; formatting inserts values into a template.

Concatenate with +

python
a = "Hello"
b = "World"
c = a + " " + b
print(c)

### Hello World

Glue with * and numbers

python
print("ab" * 3)

### ababab

f-strings (recommended)

Prefix the string with f and put variables inside { }:

python
age = 36
txt = f"My name is John, I am {age}"
print(txt)

### My name is John, I am 36

Formatting numbers in f-strings

Use a colon and a format specifier:

python
price = 59
txt = f"The price is {price:.2f} dollars"
print(txt)

### The price is 59.00 dollars

• :.2f means two decimal places.
• :> right-align, :< left-align, :^ center.

The old .format() method

python
txt = "I am {} years old".format(36)
print(txt)

### I am 36 years old

Placeholders for commas

Add commas for thousands separators:

python
txt = f"The number is {1234567:,}"
print(txt)

### The number is 1,234,567

TL;DR

• + joins strings; * repeats them.
• f-strings put values in with {name}.
• Use specifiers like :.2f and :, inside the braces.
• .format() is the older alternative.