string formatting - Explain this behaviour with Python's str.format for "general" specifier, left-aligned sign-aware zero-padding. {0:<09.6g} -


can please explain how 'general' format specifier works? i'm confused how left align 0 padding works this. don't know if bug in python or if don't understand documentation saying.

in output below confusion in last 3 blocks of printout, right column. explain, references documented format spec, why they're output that, please?

(this python 3.4.0 (v3.4.0:04f714765c13, mar 16 2014, 19:25:23) [msc v.1600 64 bit (amd64)] on win32)

test.py:

t = [8123, 0.0, 1.0, 0.799999, 1.3243423487123]  v in t:     print(str.format("{0:9g} {0:9.6g} {0:09.6g} ", v)) print()  v in t:     print(str.format("{0:>9g} {0:>9.6g} {0:>09.6g} ", v)) print()  v in t:     print(str.format("{0:=9g} {0:=9.6g} {0:=09.6g} ", v)) print()    # going on right column here??? v in t:     print(str.format("{0:<9g} {0:<9.6g} {0:<09.6g} ", v)) print()  # going on right column here??? v in t:     print(str.format("{0:<9,g} {0:<9,.6g} {0:<09,.6g} ", v)) print()   # preceding width field 0 ('0') character enables sign-aware zero-padding numeric types. # equivalent fill character of '0' alignment type of '='. # # why doesn't right column same thing above? v in t:     print(str.format("{0:0=9g} {0:0=9.6g} {0:0=09.6g} ", v)) print()

the output of :

$ python3 test.py      8123      8123 000008123          0         0 000000000          1         1 000000001   0.799999  0.799999 00.799999    1.32434   1.32434 001.32434        8123      8123 000008123          0         0 000000000          1         1 000000001   0.799999  0.799999 00.799999    1.32434   1.32434 001.32434        8123      8123 000008123          0         0 000000000          1         1 000000001   0.799999  0.799999 00.799999    1.32434   1.32434 001.32434   8123      8123      812300000  0         0         000000000  1         1         100000000  0.799999  0.799999  0.7999990  1.32434   1.32434   1.3243400   8,123     8,123     8,1230000  0         0         000000000  1         1         100000000  0.799999  0.799999  0.7999990  1.32434   1.32434   1.3243400   000008123 000008123 000008123  000000000 000000000 000000000  000000001 000000001 000000001  00.799999 00.799999 00.799999  001.32434 001.32434 001.32434

the relevant documentation following:

preceding width field 0 ('0') character enables sign-aware zero-padding numeric types. this equivalent fill character of '0' alignment type of '='.

where documentation '=' align option is:

forces padding placed after sign (if any) before digits. used printing fields in form +000000120. alignment option valid numeric types.

while < , > respectively left , right align given item:

forces field left-aligned within available space (this default objects).

forces field right-aligned within available space (this default numbers).

note use of verb forces. believe here it's stating if < specified output left-aligned. period. other implied alignments aren't considered (e.g. = implied 0 filling).

this explains examples provided: if put < output left-aligned using 09.6g should 0 padding. did expect < ignored? believe bad choice because since < explicit ought honored, while implicit = should overriden.

i don't puzzles in last example because output is equivalent first output, consistent above documentation.


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