Question

In Python, how do I specify a format when converting int to string?

More precisely, I want my format to add leading zeros to have a string
with constant length. For example, if the constant length is set to 4:

• 1 would be converted into “0001”
• 12 would be converted into “0012”
• 165 would be converted into “0165”

I have no constraint on the behaviour when the integer is greater than what can allow the given length (9999 in my example).

How can I do that in Python?

Answer 1

"%04d" where the 4 is the constant length will do what you described.

You can read about string formatting here.

Update for Python 3:

{:04d} is the equivalent for strings using the str.format method or format builtin function. See the format specification mini-language documentation.