sscanf

String Parsing (sscanf)

sscanf()

Syntax:

num = h.sscanf("string", "format", args)

Description:

A subset of the c stdio sscanf function. The formats understood are %s, %[…], %c, %lf, %f, %d, %i, %o, %x, along with numbers and the * character. Explicit strings in the format are also understood. A great deal of error checking is done to make sure the args match the format string. The function returns the actual number of args that are assigned values. The arguments must be h.ref objects.

Note that %lf is always preferred to %f since the latter truncates to floating point accuracy. Hence

from neuron import h
x = h.ref(0)
h.sscanf('0.3', '%f', x)
print(x[0])

prints: 0.300000011921

Example:

from neuron import h
s = h.ref('')
x = [h.ref(0) for i in range(20)]
y = h.ref(0)

count = h.sscanf("this is a test\n", "%s", s)
print(s[0])  # this

count = h.sscanf("this is a test\n", "%[^\n]", s)
print(s[0])  # this is a test

count = h.sscanf("this is a test\n", "%*s%s", s)
print(s[0])  # is

count = h.sscanf("this is a test\n", "%2s", s)
print(s[0])  # th

count = h.sscanf("this is a test\n", "%10s", s)
print(s[0])  # this

count = h.sscanf("this is a test\n", "%*3s%s", s)
print(s[0])  # s

count = h.sscanf("this is a test\n", "%*s%s", s)
print(s[0])  # is

count = h.sscanf("0xff 010 25", "%i%i%i", x[0], x[1], x[2])
print(x[0][0], x[1][0], x[2][0]) # 255.0 8.0 25.0

count = h.sscanf("50.75", "%d.%d", x[0], x[1])
print(x[0][0], x[1][0]) # 50.0 75.0

count = h.sscanf("30.987654321", "%f", y)
print(y[0])  # 30.9876537323

count = h.sscanf("30.987654321", "%lf", y)
print(y[0])  # 30.987654321

count = h.sscanf("A", "%c", y)
print(y[0])  # 65.0 (ASCII code for the letter A)
print('%c' % int(y[0]))  # A

count = h.sscanf("1 2 3 4 5 6 7 8 9 10", "%f%f%f%f%f%f%f%f%f%f%f", x[0], x[1], x[2],
    x[3], x[4], x[5], x[6], x[7], x[8], x[9], x[10], x[11], x[12])
print('Should only have non-zero values for x indices 0 - 9')
for i in range(13):
    print('%d %g' % (i, x[i][0]))

# the following are invalid and therefore raise a RuntimeError exception
h.sscanf('string', '%', s) # invalid format string
h.sscanf('string', '%*', s) # invalid format string
h.sscanf('string', '%c%c%c%c%c', x[0], x[1], x[2]) # error due to insufficient number of args
h.sscanf('25', '%d', s) # last entry not a pointer to a string

Note

The Python standard library does not provide a direct equivalent for h.sscanf, but consider using the Regular Expressions module re instead, which can also be used for string parsing, albeit with a different specification.