pylab的目的

Pylab combines the functionality of pyplot with the capabilities of NumPy in a single namespace, and therefore you do not need to import NumPy separately. Furthermore, if you import pylab, pyplot, and NumPy functions can be called directly without any reference to a module (namespace), making the environment more similar to Matlab.

简而言之，from pylab import *这一句话就引入了numpy、matplotlib等常用库，避免了多个import语句。一句话就创造了一个非常类似matlab的编程环境。

pylab的模块包括了许多NumPy和pyplot模块中常用的函数，方便用户快速进行计算和绘图，十分适合在IPython交互式环境中使用。

pylab模块非常单薄，查看pylab源代码可以发现此文件只有80余行，主要内容就是导入一堆包。matplot的主要内容还是在pyplot包中。

阅读以下程序，搜索一下引入的各个包的作用。

from __future__ import (absolute_import, division, print_function,

                        unicode_literals)

from matplotlib.externals import six

import sys, warnings

from matplotlib.cbook import flatten, is_string_like, exception_to_str, \

     silent_list, iterable, dedent

import matplotlib as mpl

# make mpl.finance module available for backwards compatability, in case folks

# using pylab interface depended on not having to import it

import matplotlib.finance

from matplotlib.dates import date2num, num2date,\

        datestr2num, strpdate2num, drange,\

        epoch2num, num2epoch, mx2num,\

        DateFormatter, IndexDateFormatter, DateLocator,\

        RRuleLocator, YearLocator, MonthLocator, WeekdayLocator,\

        DayLocator, HourLocator, MinuteLocator, SecondLocator,\

        rrule, MO, TU, WE, TH, FR, SA, SU, YEARLY, MONTHLY,\

        WEEKLY, DAILY, HOURLY, MINUTELY, SECONDLY, relativedelta

import matplotlib.dates  # Do we need this at all?

# bring all the  symbols in so folks can import them from

# pylab in one fell swoop

## We are still importing too many things from mlab; more cleanup is needed.

from matplotlib.mlab import griddata, stineman_interp, slopes, \

    inside_poly, poly_below, poly_between, \

    is_closed_polygon, path_length, distances_along_curve, vector_lengths

from matplotlib.mlab import window_hanning, window_none,  detrend, demean, \

     detrend_mean, detrend_none, detrend_linear, entropy, normpdf, \

     find, longest_contiguous_ones, longest_ones, \

     prctile, prctile_rank, \

     center_matrix, rk4, bivariate_normal, get_xyz_where, \

     get_sparse_matrix, dist, \

     dist_point_to_segment, segments_intersect, fftsurr, movavg, \

     exp_safe, \

     amap, rms_flat, l1norm, l2norm, norm_flat, frange,  identity, \

     base_repr, binary_repr, log2, ispower2, \

     rec_append_fields, rec_drop_fields, rec_join, csv2rec, rec2csv, isvector

import matplotlib.mlab as mlab

import matplotlib.cbook as cbook

from numpy import *

from numpy.fft import *

from numpy.random import *

from numpy.linalg import *

from matplotlib.pyplot import *

# provide the recommended module abbrevs in the pylab namespace

import matplotlib.pyplot as plt

import numpy as np

import numpy.ma as ma

# don't let numpy's datetime hide stdlib

import datetime

# This is needed, or bytes will be numpy.random.bytes from

# "from numpy.random import *" above

bytes = __builtins__['bytes']

注释之中列出了可用的命令：

This is a procedural interface to the matplotlib object-oriented

plotting library.

The following plotting commands are provided; the majority have

MATLAB |reg| [*]_ analogs and similar arguments.

.. |reg| unicode:: 0xAE

_Plotting commands

acorr - plot the autocorrelation function

annotate - annotate something in the figure

arrow - add an arrow to the axes

axes - Create a new axes

axhline - draw a horizontal line across axes

axvline - draw a vertical line across axes

axhspan - draw a horizontal bar across axes

axvspan - draw a vertical bar across axes

axis - Set or return the current axis limits

autoscale - turn axis autoscaling on or off, and apply it

bar - make a bar chart

barh - a horizontal bar chart

broken_barh - a set of horizontal bars with gaps

box - set the axes frame on/off state

boxplot - make a box and whisker plot

violinplot - make a violin plot

cla - clear current axes

clabel - label a contour plot

clf - clear a figure window

clim - adjust the color limits of the current image

close - close a figure window

colorbar - add a colorbar to the current figure

cohere - make a plot of coherence

contour - make a contour plot

contourf - make a filled contour plot

csd - make a plot of cross spectral density

delaxes - delete an axes from the current figure

draw - Force a redraw of the current figure

errorbar - make an errorbar graph

figlegend - make legend on the figure rather than the axes

figimage - make a figure image

figtext - add text in figure coords

figure - create or change active figure

fill - make filled polygons

findobj - recursively find all objects matching some criteria

gca - return the current axes

gcf - return the current figure

gci - get the current image, or None

getp - get a graphics property

grid - set whether gridding is on

hist - make a histogram

hold - set the axes hold state

ioff - turn interaction mode off

ion - turn interaction mode on

isinteractive - return True if interaction mode is on

imread - load image file into array

imsave - save array as an image file

imshow - plot image data

ishold - return the hold state of the current axes

legend - make an axes legend

locator_params - adjust parameters used in locating axis ticks

loglog - a log log plot

matshow - display a matrix in a new figure preserving aspect

margins - set margins used in autoscaling

pause - pause for a specified interval

pcolor - make a pseudocolor plot

pcolormesh - make a pseudocolor plot using a quadrilateral mesh

pie - make a pie chart

plot - make a line plot

plot_date - plot dates

plotfile - plot column data from an ASCII tab/space/comma delimited file

pie - pie charts

polar - make a polar plot on a PolarAxes

psd - make a plot of power spectral density

quiver - make a direction field (arrows) plot

rc - control the default params

rgrids - customize the radial grids and labels for polar

savefig - save the current figure

scatter - make a scatter plot

setp - set a graphics property

semilogx - log x axis

semilogy - log y axis

show - show the figures

specgram - a spectrogram plot

spy - plot sparsity pattern using markers or image

stem - make a stem plot

subplot - make one subplot (numrows, numcols, axesnum)

subplots - make a figure with a set of (numrows, numcols) subplots

subplots_adjust - change the params controlling the subplot positions of current figure

subplot_tool - launch the subplot configuration tool

suptitle - add a figure title

table - add a table to the plot

text - add some text at location x,y to the current axes

thetagrids - customize the radial theta grids and labels for polar

tick_params - control the appearance of ticks and tick labels

ticklabel_format - control the format of tick labels

title - add a title to the current axes

tricontour - make a contour plot on a triangular grid

tricontourf - make a filled contour plot on a triangular grid

tripcolor - make a pseudocolor plot on a triangular grid

triplot - plot a triangular grid

xcorr - plot the autocorrelation function of x and y

xlim - set/get the xlimits

ylim - set/get the ylimits

xticks - set/get the xticks

yticks - set/get the yticks

xlabel - add an xlabel to the current axes

ylabel - add a ylabel to the current axes

autumn - set the default colormap to autumn

bone - set the default colormap to bone

cool - set the default colormap to cool

copper - set the default colormap to copper

flag - set the default colormap to flag

gray - set the default colormap to gray

hot - set the default colormap to hot

hsv - set the default colormap to hsv

jet - set the default colormap to jet

pink - set the default colormap to pink

prism - set the default colormap to prism

spring - set the default colormap to spring

summer - set the default colormap to summer

winter - set the default colormap to winter

spectral - set the default colormap to spectral

_Event handling

connect - register an event handler

disconnect - remove a connected event handler

_Matrix commands

cumprod - the cumulative product along a dimension

cumsum - the cumulative sum along a dimension

detrend - remove the mean or besdt fit line from an array

diag - the k-th diagonal of matrix

diff - the n-th differnce of an array

eig - the eigenvalues and eigen vectors of v

eye - a matrix where the k-th diagonal is ones, else zero

find - return the indices where a condition is nonzero

fliplr - flip the rows of a matrix up/down

flipud - flip the columns of a matrix left/right

linspace - a linear spaced vector of N values from min to max inclusive

logspace - a log spaced vector of N values from min to max inclusive

meshgrid - repeat x and y to make regular matrices

ones - an array of ones

rand - an array from the uniform distribution [0,1]

randn - an array from the normal distribution

rot90 - rotate matrix k*90 degress counterclockwise

squeeze - squeeze an array removing any dimensions of length 1

tri - a triangular matrix

tril - a lower triangular matrix

triu - an upper triangular matrix

vander - the Vandermonde matrix of vector x

svd - singular value decomposition

zeros - a matrix of zeros

_Probability

normpdf - The Gaussian probability density function

rand - random numbers from the uniform distribution

randn - random numbers from the normal distribution

_Statistics

amax - the maximum along dimension m

amin - the minimum along dimension m

corrcoef - correlation coefficient

cov - covariance matrix

mean - the mean along dimension m

median - the median along dimension m

norm - the norm of vector x

prod - the product along dimension m

ptp - the max-min along dimension m

std - the standard deviation along dimension m

asum - the sum along dimension m

ksdensity - the kernel density estimate

_Time series analysis

bartlett - M-point Bartlett window

blackman - M-point Blackman window

cohere - the coherence using average periodiogram

csd - the cross spectral density using average periodiogram

fft - the fast Fourier transform of vector x

hamming - M-point Hamming window

hanning - M-point Hanning window

hist - compute the histogram of x

kaiser - M length Kaiser window

psd - the power spectral density using average periodiogram

sinc - the sinc function of array x

_Dates

date2num - convert python datetimes to numeric representation

drange - create an array of numbers for date plots

num2date - convert numeric type (float days since 0001) to datetime

_Other

angle - the angle of a complex array

griddata - interpolate irregularly distributed data to a regular grid

load - Deprecated--please use loadtxt.

loadtxt - load ASCII data into array.

polyfit - fit x, y to an n-th order polynomial

polyval - evaluate an n-th order polynomial

roots - the roots of the polynomial coefficients in p

save - Deprecated--please use savetxt.

savetxt - save an array to an ASCII file.

trapz - trapezoidal integration

__end

.. [*] MATLAB is a registered trademark of The MathWorks, Inc.