Python : Could not cast a numpy array into a string

Question

I wrote a code which is meant to replace a tag from a string with a number extracted from an array.

This is part of a bigger project but I only isolated the problematic part

# import numpy as np
time_vect = np.arange(0, 10, 1)
string = "T= <T>"
for i in range(0, len(time_vect),1):
    string = string.replace("<T>", str(time_vect[i]))
    print(string)

However the replace function seems to totally ignore the value. When I run the code I get this output :

T= 0
T= 0
T= 0
T= 0
T= 0
T= 0
T= 0
T= 0
T= 0
T= 0

When I assign the value manually, I get the expected result

>> print(string.replace("<T>", str(time_vect[3])))
T= 3

I tried to convert the numpy.int32 type into native int type but it did not solve the problem

string = string.replace("<T>", str(time_vect[i].item()))

I could not find any leads on the net so I would be thankful if I could get some support :)

You are replacing the "<T>" in the first iteration, after that the replace function can't find it again. — Mhamed Bendenia
– Mhamed Bendenia, Commented Jul 14, 2021 at 10:47

Mhamed Bendenia · Accepted Answer · 2021-07-14 10:52:52Z

1

Same as @Vulwsztyn, without an intermediate variable :

time_vect = np.arange(0, 10, 1)
string = "T= <T>"
for i in range(0, len(time_vect),1):
    print(string.replace("<T>", str(time_vect[i])))

answered Jul 14, 2021 at 10:52

Mhamed Bendenia

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1 Comment

Nazim Yakhou Over a year ago

Well noted ! Thanks

Vulwsztyn · Accepted Answer · 2021-07-14 10:47:25Z

0

You cannot reassing string in the loop. After the first iteration, your string no longer contains <T> so there is nothing to replace it is "T= 0", so replacing <T> does nothing.

import numpy as np
time_vect = np.arange(0, 10, 1)
string = "T = <T>"
for i in range(0, len(time_vect),1):
    s = string.replace("<T>", str(time_vect[i]))
    print(s)

answered Jul 14, 2021 at 10:47

Vulwsztyn

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