CODEWITHSUNDEEP
python
Vingtoft
Vingtoft

Reputation: 14606

Assign and increment value on one line

Is it possible to assign a value and increment the assigned value on the same line in Python?

Something like this:

x = 1
a = x
b = (x += 1)
c = (x += 1)

print a
print b
print c

>>> 1
>>> 2
>>> 3

I need it in a context where I'm creating an Excel sheet:

col = row = 1
ws.cell(row=row, column=col).value = "A cell value"
ws.cell(row=row, column=(col += 1)).value = "Another cell value"
ws.cell(row=row, column=(col += 1)).value = "Another cell value"

Upvotes: 11

Views: 13328

Answers (7)

BSalita
BSalita

Reputation: 8931

Increment within an if statement returning when a boundary is being exceeded. I found this idiom to be simple and clean when a state machine required dozens of increment and tests.

if (i := i+1) >= limit: return i

Upvotes: 0

Tomerikoo
Tomerikoo

Reputation: 19414

Since Python 3.8, you can use the walrus operator which was introduced in PEP-572. This operator creates an assignment expression. So you can assign new values to variables, while returning the newly assigned value:

>>> print(f"{(x := 1)}")
1
>>> x
1
>>> print(f"{(x := x+1)}")
2
>>> x
2
>>> b = (x := x+1)
>>> b, x
(3, 3)

In the context of your question, this will work:

col = row = 1
ws.cell(row=row, column=col).value = "A cell value"
ws.cell(row=row, column=(col := col+1)).value = "Another cell value"
ws.cell(row=row, column=(col := col+1)).value = "Another cell value"

Upvotes: 7

Tomerikoo
Tomerikoo

Reputation: 19414

* self-answer by the OP that was edited into the question:

It's not possible, but I have created an easy fix:

col = row = 1

def increment_one():
    global col
    col += 1
    return col

ws.cell(row=row, column=col).value = "A cell value"
ws.cell(row=row, column=increment_one()).value = "Another cell value"
ws.cell(row=row, column=increment_one()).value = "Another cell value"

Upvotes: 0

poke
poke

Reputation: 387617

No that’s not possible in Python versions < 3.8.

Assignments (or augmented assignments) are statements and as such may not appear on the right-hand side of another assignment. You can only assign expressions to variables.

The reason for this is most likely to avoid confusions from side effects which are easily caused in other languages that support this.

However, normal assignments do support multiple targets, so you can assign the same expression to multiple variables. This of course still only allows you to have a single expression on the right-hand side (still no statement). In your case, since you want b and x to end up with the same value, you could write it like this:

b = x = x + 1
c = x = x + 1

Note that since you’re doing x = x + 1 you are no longer using an augmented assignment and as such could have different effects for some types (not for integers though).

Upvotes: 10

Rufat
Rufat

Reputation: 692

You can use range, iter and next:

from openpyxl import Workbook

wb = Workbook()
ws = wb.active

col = row = 1
iter_int = iter(range(col, col + 100))

ws.cell(row=row, column=next(iter_int)).value = "A cell value"
ws.cell(row=row, column=next(iter_int)).value = "Another cell value"
ws.cell(row=row, column=next(iter_int)).value = "Another cell value"

wb.save("cell_values.xlsx")

Upvotes: 0

Lafexlos
Lafexlos

Reputation: 7735

Not a pretty one but you can do something like this.

x = 1
a = x
x = b = x+1
x = c = x+1

>>> print a,b,c 
>>> 1,2,3

>>>print id(a),id(b),id(c),id(x)
>>>31098952 31098928 31098904 31098904

Upvotes: 4

wolfsgang
wolfsgang

Reputation: 894

You can do it using a function,here I use the lambda function. There is no exact python equivalent of ++x or x++ in c.

inc =lambda t: t+1
x = 1
a = x
b,x=inc(x),x+1
c,x = inc(x),x+1

print a
print b
print c

Upvotes: 2

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