Python3中一步实现变量自增赋值？为何a++语法报错？

Hey there! Let's unpack your problem clearly.

Why you're getting that SyntaxError #

Unlike languages like C, Java, or JavaScript, Python doesn't have the ++ (or --) operator at all. This is a deliberate design choice—Python prioritizes readability and avoids ambiguous syntax. The ++ operator in other languages has two distinct behaviors (prefix: increment first then use the value; suffix: use the value first then increment), which can lead to confusion. Python opted to skip this entirely, so writing z = a++ is just invalid syntax to the interpreter.

Your original working code already does exactly what you want in a clear, Pythonic way:

a = 90
z = a + 1
print(z)  # Outputs 91

How to mimic the ++ behavior in Python #

If you're looking to replicate the two common behaviors of ++ from other languages, here's how to do it properly in Python:

1. Suffix ++ (use the original value first, then increment a) #

This is what you might have thought z = a++ would do—assign a's current value to z, then increase a by 1:

a = 90
z = a  # Assign original value to z
a += 1  # Increment a by 1
print(z)  # Outputs 90
print(a)  # Now a is 91

2. Prefix ++ (increment a first, then use the new value) #

If you want to increment a first and then assign the updated value to z:

a = 90
a += 1  # Increment a first
z = a  # Assign the new value to z
print(z)  # Outputs 91

3. Just increment a (no assignment to another variable) #

If you only need to increase a by 1 (like a++ on its own), use Python's augmented assignment—it's the closest equivalent:

a = 90
a += 1  # Same effect as a = a + 1, but cleaner
print(a)  # Outputs 91

内容的提问来源于stack exchange，提问作者m.d venkatesh