SyntaxError: invalid syntax

Python met a word or symbol it didn't expect there, and can't say more. It's usually one of these, on the line it points to or the one above.

• A Python word used as a name. class, pass, from, in, is, def, return, global and lambda belong to Python: pass = "1234" → password = "1234".
• A space in a name. my score = 10 → my_score = 10.
• Text without quotes. name = Ada Lovelace → name = "Ada Lovelace".
• Two values with nothing between them. greeting = "Hi " name → greeting = "Hi " + name, and if x 5: → if x == 5:.
• A command, not code. pip install requests and python main.py go in a terminal, not in the program: delete the line. In code copied from the Python shell, delete the >>> at the start of each line.
• Symbols from other languages. i++ → i += 1, && → and, || → or, ! → not, === → ==. Comments start with #, not //.
• Words from other languages. function add(a, b): → def add(a, b):, for item of items: → for item in items:, x => x * 2 → lambda x: x * 2. Python needs no then or do, and no { } around a block: a colon and indented lines.
• A for loop without in. for i range(5): → for i in range(5):.
• An else or elif away from its if. It comes straight after the if block, at the same indentation, and else comes last.
• Two statements on one line. print("a") print("b"): put each on its own line.
• Something left out. x = 5 + → x = 5 + 1, and print(1,, 2) → print(1, 2).

A name can't start with a digit, and a number can't have letters stuck to it. Spell the name out, or put an operator between the number and the name: 5 * apples.

2nd_place = "Bo"
print(2nd_place)

SyntaxError: invalid decimal literal

second_place = "Bo"
print(second_place)

Bo

There's a closing bracket with no opening one before it, often an extra one at the end of the line.

print("Hi"))

SyntaxError: unmatched ')'

print("Hi")

Hi

That's Python 2. In Python 3, print is a function: put what it prints in brackets.

print "Hello"

SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

print("Hello")

Hello

return only works inside a function. Usually the line lost its indentation: put it back under the def.

def add(a, b):
    total = a + b
return total

print(add(2, 3))

SyntaxError: 'return' outside function

def add(a, b):
    total = a + b
    return total

print(add(2, 3))

5

break and continue only work inside a for or while loop. Indent them inside it.

for n in [3, 7, 9]:
    print(n)
if n == 7:
    break

SyntaxError: 'break' outside loop

for n in [3, 7, 9]:
    print(n)
    if n == 7:
        break

3
7

A whole number can't start with 0. Write 8, or keep the zero in text: "08".

month = 08
print(month)

SyntaxError: leading zeros in decimal integer literals are not permitted; use an 0o prefix for octal integers

month = 8
print(month)

8

A try block needs an except (or finally) block right after it, at the same indentation.

try:
    number = int("42")
print(number)

SyntaxError: expected 'except' or 'finally' block

try:
    number = int("42")
except ValueError:
    number = 0
print(number)

42

In a call, plain values come first and name=value ones last.

print(sep="-", "a", "b")

SyntaxError: positional argument follows keyword argument

print("a", "b", sep="-")

a-b

A \ at the very end of a line carries it on to the next; anywhere else it's an error. To divide, use /.

x = 10 \ 2
print(x)

SyntaxError: unexpected character after line continuation character

x = 10 / 2
print(x)

5.0

Every { in an f-string needs its }, with a value or name between them.

name = "Ada"
print(f"Hi {name")

SyntaxError: f-string: expecting '}'

name = "Ada"
print(f"Hi {name}")

Hi Ada

Python writes it the other way round: from module import name.

import sqrt from math
print(sqrt(16))

SyntaxError: Did you mean to use 'from ... import ...' instead?

from math import sqrt
print(sqrt(16))

4.0

In a def, parameters with a default value go after the ones without.

def greet(greeting="Hi", name):
    print(greeting, name)

greet(name="Ada")

SyntaxError: parameter without a default follows parameter with a default

def greet(name, greeting="Hi"):
    print(greeting, name)

greet("Ada")

Hi Ada

To catch several errors with one except, put them in brackets.

try:
    number = int("abc")
except ValueError, TypeError:
    number = 0
print(number)

SyntaxError: multiple exception types must be parenthesized

try:
    number = int("abc")
except (ValueError, TypeError):
    number = 0
print(number)

0

A value chosen with if on one line needs an else part too: "big" if x > 3 else "small".

x = 5
size = "big" if x > 3
print(size)

SyntaxError: expected 'else' after 'if' expression

x = 5
size = "big" if x > 3 else "small"
print(size)

big