问题
I am trying to print the results of some previous calculations, and am having some issues using Numpy to print the values out of an array correctly. Each of the variables in the loop is defined by calculations previously, and it needs to run thru the speed permutations to get the data for each speed in .5kn increments.
The code in question is:
print('Speed Dependent factors and residuary resistance coefficents')
#output table
#table header
#Top Row
print('V'.center(12),end='') #the end='' prevents a new line'
print('V'.center(12),end='')
print('FN'.center(12),end='')
print('CRstdmin'.center(12),end='')
print('kFrmin'.center(12),end='')
print('CRBTmin'.center(12),end='')
print('CRmin'.center(12),end='')
print('CRstdmean'.center(12),end='')
print('kFrmean'.center(12),end='')
print('CRBTmean'.center(12),end='')
print('CRmean'.center(12),)
#Second Row
print('knots'.center(5),end='')
print('m/s'.center(12), end='')
print('--'.center(12), end='')
print('--'.center(12), end='')
print('--'.center(12), end='')
print('--'.center(12), end='')
print('10^-3'.center(12), end='')
print('--'.center(12), end='')
print('--'.center(12), end='')
print('--'.center(12), end='')
print('10^-3'.center(12))
print('-'*135)
#loop for table cell values
kFrmin=round(kFrmin,5)
for i in range(len(VS)):
print('{:12.1f}'.format(Vskn[i]), end='')
print('{:12.3f}'.format(VS[i]), end='')
print('{:12.4f}'.format(FN[i]), end='')
print('{:12.4f}'.format(CRstdmin[i]), end='')
print('{:12.4f}'.format(kFrmin), end='')
print('{:12.4f}'.format(CRBTmin[i]), end='')
print('{:12.4f}'.format(CRmin[i]), end='')
print('{:12.4f}'.format(CRstdm[i]), end='')
print(kFrm, end="")
np.set_printoptions()
#print('{:12.4f}'.format(kFrm), end='')
print('{:12.4f}'.format(CRBTm[i]), end='')
print('{:12.4f}'.format(CRm[i]),)
回答1:
Right, ok, I think I understand what the goal is here. What you have are a whole bunch of 1D arrays - meaning each represents a vector (as compared to a matrix or tensor). Your goal is to print those values in a table in a very specific way. It seems to me that the quick fix is to change print(kFrm, end="") to use the same convention as all the other prints: print('{:12.4f}'.format(kFrm[i]), end=''). Get rid of the np.set_printoptions() call after that.
Why is this happening? I believe your current code is partially based on a previous conversation, but that was without the full context. kFrm is a vector just like all of the other variables you're working with, so you just want to print the i'th value of that vector in that row. If you had wanted to print the entire vector as a single row, then you'd use the code as it is right now.
As a side note, you may be able to save yourself some headache (or, arguably, introduce more of a headache) by using pandas. If you do, you could do something like below. The only catch is that you can't name columns the same thing, so you have to name your first and second columns V and VS, instead of V and V:
# At the top of your file
import pandas as pd
# All the other stuff
...
kFrmin = round(kFrmin,5)
# Create the data frame,
# mapping name to vector.
# Each entry here represents
# a column in the eventual output
dataframe = pd.DataFrame({
"V": Vskn,
"VS": VS,
"FN": FN,
"CRstdmin": CRstdmin,
"kFrmin": float(kFrmin), # kFrmin is defined as an int in your
"CRBTmin": CRBTmin, # code, we need a float
"CRmin": CRmin,
"CRstdmean": CRstdm,
"kFrmean": kFrm,
"CRBTmean": CRBTm,
"CRmean": CRm,
})
# Set some options for printing
with pd.option_context(
"display.max_columns", 11, # Display all columns
"display.expand_frame_repr", False, # Don't wrap columns
"display.float_format", "{:>12.4f}".format, # Default to 4 digits of precision,
): # pad to 12 places
df_str = dataframe.to_string(
index=False, # Don't print the dataframe index
formatters={
"V": "{:>12.1f}".format, # V uses 1 digit of precision
"VS": "{:>12.3f}".format, # VS uses 3 digits of precision
}
)
# Everything from here... (see below)
df_str_rows = df_str.split("\n") # Split up the original table string
# Create the unit row values
unit_row = ["knots", "m/s", "--", "--", "--", "--", "10^-3", "--", "--", "", "10^-3"]
# Pad them using right justification
pd_cspace = pd.get_option("column_space")
unit_row_str = (unit_row[0].rjust(pd_cspace) +
''.join(r.rjust(pd_cspace + 1) for r in unit_row[1:]))
# Insert that new row back into the table string
df_str_rows.insert(1, unit_row_str)
df_str_rows.insert(2, "-" * len(unit_row_str))
df_str = '\n'.join(df_str_rows)
# ... to here was just to include the extra unit row
# and the dash line separating the table. You could ignore
# it if you don't care about those
# Ok now print
print('Speed Dependent factors and residuary resistance coefficents')
print(df_str)
This gives you:
Speed Dependent factors and residuary resistance coefficents
V VS FN CRstdmin kFrmin CRBTmin CRmin CRstdmean kFrmean CRBTmean CRmean
knots m/s -- -- -- -- 10^-3 -- -- -- 10^-3
----------------------------------------------------------------------------------------------------------------------------------------------
15.0 7.717 0.1893 0.8417 1.0000 0.1870 0.7645 0.8417 1.0000 0.1786 0.7302
15.5 7.974 0.1956 0.8928 1.0000 0.1984 0.8110 0.8928 1.0000 0.1895 0.7746
16.0 8.231 0.2019 0.9502 1.0000 0.2111 0.8631 0.9502 1.0000 0.2017 0.8243
16.5 8.488 0.2083 1.0138 1.0000 0.2253 0.9208 1.0138 1.0000 0.2152 0.8795
17.0 8.746 0.2146 1.0837 1.0000 0.2408 0.9843 1.0837 1.0000 0.2300 0.9401
17.5 9.003 0.2209 1.1598 1.0000 0.2577 1.0535 1.1598 1.0000 0.2461 1.0062
18.0 9.260 0.2272 1.2422 1.0000 0.2760 1.1283 1.2422 1.0205 0.2690 1.0997
18.5 9.517 0.2335 1.3308 1.0000 0.2957 1.2088 1.3308 1.0508 0.2968 1.2132
19.0 9.774 0.2398 1.4257 1.0000 0.3168 1.2950 1.4257 1.0829 0.3276 1.3394
19.5 10.032 0.2461 1.5269 1.0000 0.3393 1.3869 1.5269 1.1167 0.3619 1.4793
20.0 10.289 0.2524 1.6343 1.0000 0.3631 1.4845 1.6343 1.1525 0.3997 1.6340
Why go through all of this trouble with pandas? I'd argue we do so because pandas and numpy have done a massive amount of work to make things print nicely. The more we can leverage that work, the more confident we can be that our output will be robust and really look good. However, you could also decide to ignore the second half of this answer and I really wouldn't hold it against you.
来源：https://stackoverflow.com/questions/64670207/printing-a-numpy-array