I have a string like
a = "X1+X2*X3*X1"
b = {"X1":"XX0","X2":"XX1","X0":"XX2"}
I want to replace the substring 'X1,X2,X3' using dict b.
However, when I replace using the below code,
for x in b:
a = a.replace(x,b[x])
print(a)
'XXX2+XX1*X3'
Expected result is XX0 + XX1*X3*XX0
I know it is because the substring is replaced in a loop, but I don't know how to solve it.
You can use the repl parameter of re.sub:
import re
re.sub('X\d', lambda x: b.get(x.group(), x.group()), a)
output:
'XX0+XX1*X3*XX0'
You can create a pattern with '|' then search in dictionary transform like below.
Try this:
import re
a = "X1+X2*X3*X1"
b = {"X1":"XX0","X2":"XX1","X0":"XX2"}
pattern = re.compile("|".join(b.keys()))
out = pattern.sub(lambda x: b[re.escape(x.group(0))], a)
Output:
>>> out
'XX0+XX1*X3*XX0'
The reason for this is beacuse you are replacing the same string multiple times, so behind the scenes (or between the iterations) there are a few more switches in the middle that you probably don't see (unless debugging this code). Please note that dictionary keys are not ordered, so you cannot assume what's replaced when. I suggest you use template
With just built-in functions. The given b dictionary contains cycles between keys and values, so used the f-string notation to perform the substitutions. To escape the {} one should double them {{}}, used for repeated substitution. The enumerate is needed to get unique keys in the new dictionary, so no more cycles.
a = "X1+X2*X3*X1"
b = {"X1":"XX0","X2":"XX1","X0":"XX2"}
new_dict = {}
for i, k in enumerate(b):
sub_format = f'{k}' + f'{i}'
new_dict[sub_format] = b[k]
a = a.replace(k, f'{{{sub_format}}}')
print(a.format(**new_dict))
Output
XX0+XX1*X3*XX0