CODEWITHSUNDEEP
pythonconcatenation
Mark T
Mark T

Reputation: 155

Concatenate Strings and Variables of two conditions while iterating in python

I have an iteration over a dataframe, but for the example here I used a list.

seq = [0, -1, 0, 1, 2, 1, 0, -1, -2, -3, -4, -5, -4, -3, -2, -1]
box = []

for i in range(1, len(seq)):
    if seq[i] > seq[i-1]:
        box.append(seq[i])
    else:
        box.append(seq[i-1]+10)

box

Now i would like to add to each appended value a string prefix like this:
For all values from the If statement letter 'A-'
For all values from else statement letter 'B-'

My desired output is:

[B-10, A-0, A-1, A-2, B-12, B-11, B-10......

I tried it with .join and with simple comma or + inside the append method, but none of it works. Any suggestions how to accomplish this ?

Upvotes: 0

Views: 128

Answers (2)

NewPythonUser
NewPythonUser

Reputation: 351

Idiotic one-liner:

box = map(lambda p: "A-" + str(p[1]) if p[1] > p[0] else "B-" + str(p[0] + 10), [(seq[i-1], seq[i]) for i,_ in enumerate(seq[:])][1:])

But in all seriousness just use string concatenation, but convert the integer value to string before concatenating:

seq = [0, -1, 0, 1, 2, 1, 0, -1, -2, -3, -4, -5, -4, -3, -2, -1]
box = []

for i in range(1, len(seq)):
    if seq[i] > seq[i-1]:
        box.append("A-" + str(seq[i]))
    else:
        box.append("B-" + str(seq[i-1]+10))

print (box)

Upvotes: 0

Nico Müller
Nico Müller

Reputation: 1874

You can use the f-string literal to add the related letter:

seq = [0, -1, 0, 1, 2, 1, 0, -1, -2, -3, -4, -5, -4, -3, -2, -1]
box = []

for i in range(1, len(seq)):
    if seq[i] > seq[i-1]:
        box.append(f"A-{seq[i]}")
    else:
        box.append(f"B-{seq[i-1]+10}")

print(box)
OUT: ['B-10', 'A-0', 'A-1', 'A-2', 'B-12', 'B-11', 'B-10', 'B-9', 'B-8', 'B-7', 'B-6', 'A--4', 'A--3', 'A--2', 'A--1']

Upvotes: 3

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